EP4602156A2 - Compositions, méthodes et systèmes de modification d'adn - Google Patents
Compositions, méthodes et systèmes de modification d'adnInfo
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- EP4602156A2 EP4602156A2 EP23878197.5A EP23878197A EP4602156A2 EP 4602156 A2 EP4602156 A2 EP 4602156A2 EP 23878197 A EP23878197 A EP 23878197A EP 4602156 A2 EP4602156 A2 EP 4602156A2
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- C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
- C12N15/09—Recombinant DNA-technology
- C12N15/87—Introduction of foreign genetic material using processes not otherwise provided for, e.g. co-transformation
- C12N15/90—Stable introduction of foreign DNA into chromosome
- C12N15/902—Stable introduction of foreign DNA into chromosome using homologous recombination
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- C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
- C12N15/09—Recombinant DNA-technology
- C12N15/11—DNA or RNA fragments; Modified forms thereof; Non-coding nucleic acids having a biological activity
- C12N15/111—General methods applicable to biologically active non-coding nucleic acids
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- C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
- C12N15/09—Recombinant DNA-technology
- C12N15/63—Introduction of foreign genetic material using vectors; Vectors; Use of hosts therefor; Regulation of expression
- C12N15/79—Vectors or expression systems specially adapted for eukaryotic hosts
- C12N15/85—Vectors or expression systems specially adapted for eukaryotic hosts for animal cells
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- C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
- C12N15/09—Recombinant DNA-technology
- C12N15/87—Introduction of foreign genetic material using processes not otherwise provided for, e.g. co-transformation
- C12N15/90—Stable introduction of foreign DNA into chromosome
- C12N15/902—Stable introduction of foreign DNA into chromosome using homologous recombination
- C12N15/907—Stable introduction of foreign DNA into chromosome using homologous recombination in mammalian cells
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- C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
- C12N9/14—Hydrolases (3)
- C12N9/16—Hydrolases (3) acting on ester bonds (3.1)
- C12N9/22—Ribonucleases [RNase]; Deoxyribonucleases [DNase]
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- C07K—PEPTIDES
- C07K2319/00—Fusion polypeptide
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- C07—ORGANIC CHEMISTRY
- C07K—PEPTIDES
- C07K2319/00—Fusion polypeptide
- C07K2319/01—Fusion polypeptide containing a localisation/targetting motif
- C07K2319/09—Fusion polypeptide containing a localisation/targetting motif containing a nuclear localisation signal
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- C07—ORGANIC CHEMISTRY
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- C07K2319/00—Fusion polypeptide
- C07K2319/80—Fusion polypeptide containing a DNA binding domain, e.g. Lacl or Tet-repressor
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- C12N2310/00—Structure or type of the nucleic acid
- C12N2310/10—Type of nucleic acid
- C12N2310/20—Type of nucleic acid involving clustered regularly interspaced short palindromic repeats [CRISPR]
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- C12N2800/00—Nucleic acids vectors
- C12N2800/90—Vectors containing a transposable element
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/30—Against vector-borne diseases, e.g. mosquito-borne, fly-borne, tick-borne or waterborne diseases whose impact is exacerbated by climate change
Definitions
- the present invention relates to compositions, methods, and systems for DNA modification.
- the present invention provides compositions, and systems comprising a TnpA protein, a TnpB protein, an IscB protein, or a combination thereof, and methods using thereof.
- COLUM_41375_601_SequenceListing.xml (Size: 811,855 bytes; and Date of Creation: October 11, 2023) is herein incorporated by reference in its entirety.
- IS Insertion sequences
- Insertion sequences of 1S200/IS605 family contain the genes for their transposition and its regulation: a TnpA transposase, which is essential for mobilization, and an accessory gene, e.g., TnpB or IscB, which are evolutionary ancestors to CRISPR-Cas9 and Casl2 enzymes. These transposon components offer an expansion on genome editing options.
- engineered systems comprising a TnpA protein, a TnpB protein, an IscB protein, or a combination thereof.
- the systems comprise at least one guide RNA, or one or more nucleic acids encoding thereof, wherein the at least one guide RNA is complementary to at least a portion of a target nucleic acid.
- the systems comprise a TnpA protein, a TnpB protein, an IscB protein, or a combination thereof, or one or more nucleic acids encoding thereof and optionally, at least one guide RNA, or one or more nucleic acids encoding thereof, wherein the at least one guide RNA is complementary to at least a portion of a target nucleic acid.
- the TnpA, TnpB, and IscB protein is derived from Geobacillus stearothermophilus, Clostridium botulinum, Clostridium senegalense, or Clostridioides difficile.
- the TnpA protein, TnpB protein, IscB protein are derived from an IS607-family element.
- the TnpA protein, TnpB protein, IscB protein are derived from an IS200/IS605-family element.
- the TnpA protein comprises any amino acid sequence having at least 70% identity to any of SEQ ID NO: 11, 21, 25, and 38-41. In some embodiments, the TnpA protein comprises any amino acid sequence of any of SEQ ID NO: 11 , 21 , 25, and 38-41.
- the TnpB protein comprises any amino acid sequence having at least 70% identity to any of SEQ ID NOs: 1-4, 6-9, 17, 22-24, 30-37, and 42-50. In some embodiments, the TnpB protein comprises any amino acid sequence of any of SEQ ID NOs: 1-4, 6-9, 17, 22-24, 30-37, and 42-50.
- the IscB protein comprises any amino acid sequence having at least 70% identity to any of SEQ ID NO: 5 or 10. In some embodiments, the IscB protein comprises any amino acid sequence of any of SEQ ID NO: 5 or 10.
- the system comprises a TnpA protein having an amino acid sequence with at least 70% identity to any of SEQ ID NO: 11, 21, 25, and 38-41 , or a nucleic acid encoding thereof, a TnpB protein having an amino acid sequence with at least 70% identity to any of SEQ ID NOs: 1-4, 6-9, 17, 22-24, 30-37, and 42-50, or a nucleic acid encoding thereof, an IscB protein having an amino acid sequence with at least 70% identity to SEQ ID NO: 5 or 10, or a nucleic acid encoding thereof, or a combination thereof; and optionally, at least one guide RNA, or a nucleic acid encoding thereof, wherein the at least one guide RNA is complementary to at least a portion of a target nucleic acid.
- the system comprises, consists of, or consists essentially of a TnpA protein. In some embodiments, the system comprises, consists of, or consists essentially of a TnpA protein and at least one guide RNA.
- the system comprises, consists of, or consists essentially of a TnpB protein. In some embodiments, the system comprises, consists of, or consists essentially of a TnpB protein and at least one guide RNA.
- the system comprises a TnpA protein and a DNA nuclease capable of inducing site-specific single or double strand breaks, or one or more nucleic acids encoding thereof.
- the DNA nuclease is a CRISPR/Cas nuclease, an RNA- guided DNA nuclease encoded by insertion sequences, and/or a homing endonuclease.
- the CRISPR/Cas nuclease is Cas9 or Casl2.
- the DNA nuclease encoded by insertion sequences is IscB, IsrB, TnpB, or Fanzor.
- the homing endonuclease is ISce-I, ICre-I, or HO.
- the system comprises a TnpA protein and at least one of the TnpB protein or IscB protein, or one or more nucleic acids encoding thereof.
- the system further comprises at least one guide RNA.
- FIG. 5B TnpB promotes robust transposon retention at the donor site, as assessed by blue-white colony screening. Representative plating results are shown from experiments that included the indicated components. M, TnpA (Y125A) mutant; dTnpB, D196A mutation. FIG. 5C, Quantification of the data from FIG. 5B across multiple experimental replicates.
- RNA-guided DNA cleavage of the donor joint initiates homologous recombination with the sister chromosome that still contains the IS element, thus rapidly restoring the transposon at the original donor site; the absence of TnpB/IscB leads to permanent transposon loss after cell division.
- TnpB/IscB can also cleave sister chromosomes lacking the newly integrated IS element after transposition to a new target site, facilitating further spread.
- the transposon is shown in dark blue; the TAM is shown in yellow, and light blue rectangles represent regions complementary to the guide portion of the coRNA.
- FIGS. 6A-6D show bioinformatic analyses of IscB and TnpB homologs.
- FIG 6A Phylogenetic tree of IscB and IsrB protein homologs; IscB contain HNH and RuvC nuclease domains, whereas IsrB lacks the HNH nuclease.
- Genetic neighborhood analyses demonstrate that most homologs are encoded proximal to a predicted oiRNA (inner ring), whereas the vast majority do not reside near a predicted TnpA transposase gene (outer ring). The GsflscB homolog used in this study is indicated. Bootstrap values are indicated for major nodes.
- FIG. 1 Phylogenetic tree of IscB and IsrB protein homologs
- IscB contain HNH and RuvC nuclease domains
- IsrB lacks the HNH nuclease.
- Genetic neighborhood analyses demonstrate that most homologs are encoded
- FIG. 6B Schematic of a non-autonomous IS element encoding IscB and its associated coRNA; a structural covariation model is shown in the inset The red rectangle and dotted black line indicate the transposon boundaries, and the guide portion of the coRNA is shown in blue. LE and RE, transposon left end and right end.
- FIG. 6C Orientation bias of the nearest upstream ORFs to the indicated protein-coding gene (iscB, tnpB or IS 630), demonstrating that IS elements encoding IscB are preferentially integrated (or retained) in an orientation matching that of the upstream gene.
- the y-axis indicates the frequency of ORFs containing the same orientation, at a distance from the gene start codon defined by the x-axis.
- FIG. 242 bp represents the average length of IscB- associated toRNAs upstream of IscB ORF.
- the spike at ⁇ O-bp for TnpB corresponds to IS elements that encode adjacent/overlapping tnpA and tnpB genes.
- IS630 transposase genes are included as a representative gene from unrelated transposable elements.
- FIG. 6D Phylogenetic tree of TnpB homologs. Genetic neighborhood analyses demonstrate that most homologs are encoded proximal to a predicted coRNA (inner ring), whereas the vast majority do not reside near a predicted TnpA transposase gene (outer rings). Bootstrap values are indicated for major nodes.
- TnpB homologs are associated with two unrelated transposase families, tyrosine transposases (TnpA ( ⁇ )) and serine transposases (TnpA (S)) in bacteria.
- GrtTnpB homologs used in this study are highlighted, along with the predicted structures of their associated toRNAs, based on covariance modeling. ISGstl TnpBl was not experimentally active and ooRNA did not show strong covariation in structure and was therefore omitted.
- FIGS. 7A-7E show classification of IS605-family elements encoded by G. stearothermophilus strain DSM458.
- FIG. 7 A DNA multiple sequence alignment of transposon left ends for IS200/IS605-family elements from G. stearothermophilus. The weblogo (top) is built from 47 unique elements and one representative sequence from each family (SEQ ID NOs: 215-219 for ISGstl, ISGst3, ISGst2, ISGstS, and ISGst4, respectively) is shown below, with the TAM shown in yellow and DNA guide sequences shown in red as indicated. Nucleotides highlighted in black exhibit covarying mutations, relative to ISG.sV/.
- FIG. 7D Phylogenetic tree of ISGsf elements based on the transposon right end, shown as in FIG. 7B but with TEM sequence in lieu of TAM.
- FIG. 7E Schematic of PATEs (palindrome associated transposable elements) related to ISGstl and ISGs/5, which contain similar transposon ends but no protein-coding genes. The percent sequence identity between shaded regions (black) is shown, as are the genomic accession IDs and coordinates.
- FIGS. 8A-8G show specificity and efficiency of transposon DNA excision by TnpA.
- FIG. 8A Schematic of heterologous transposon excision assay in£'. coli. Plasmids encode TnpA and mini-transposon (Mini-Tn) substrates, whose loss is monitored by PCR using the indicated primers. The expected sizes of PCR products generated from donor joints that are produced upon re-ligation of flanking sequences are shown, for both ISGstl andH. pylori 1S60S. FIG.
- TnpA homologs do not cross-react with distinct IS elements, as assessed by analytical PCR
- Cell lysates were tested after overnight expression of TnpA in combination with a mini-Tn substrate, from either G. stearothermophilus (G) or H. pylori (H), and PCR products were resolved by agarose gel electrophoresis.
- M refers to catalytically inactive mutants. Note that/fpjTnpA is substantially more active for DNA excision than GstTnpA under the tested conditions.
- U unexcised
- E excised.
- FIG. 8C Schematic of qPCR assay to quantify excision frequencies, in which one of the two primers anneals directly to the donor joint formed upon mini-Tn excision and re-ligation.
- FIG. 8D Comparison of simulated excision frequencies, generated by mixing clonally excised and unexcised lysate in known ratios, versus experimentally determined integration efficiencies measured by qPCR
- FIG. 8E qPCR-based quantification of TnpA- mediated excision of an TSGstl mini-Tn substrate in E. coli.
- Mock refers to a cloned excision product; M denotes a TnpA mutant ( ⁇ 125 A); ND, not detected above a 0.0001% threshold.
- FIG. 8F Schematic of mini-Tn ISGsr2 element, highlighting the subterminal palindromic transposon ends located on the top strand (top).
- Transposon-adjacent and transposon-encoded motifs (TAM and TEM) are shown in yellow and orange, respectively; DNA guides are shown in red, and their putative base-pairing interactions are indicated; dotted lines indicate transposon boundaries and thus the sites of ssDNA cleavage and re-ligation.
- LE is SEQ ID NO: 204;
- RE is SEQ ID NO: 205.
- Sanger sequencing (SEQ ID NO: 225) of excision events confirm the identity of the expected donor joint product formed upon transposon loss (bottom).
- FIGS. 9A-9C show mating-out assay to monitor transposition of ISGrt2.
- FIG. 9 A Schematic of mating-out assay, in which transposition events into the F-plasmid are monitored via drug selection.
- E. coli donor cells carrying an F-plasmid were transformed with a plasmid encoding TnpA and ISG5t2-derived mini-Tn. After induction of TnpA, conjugation was used to transfer the F-plasmid into the recipient strain, and transposition events were quantified by selecting for recipient cells (Rif 8 ) containing spectinomycin (F + ) and kanamycin (mini-Tn 4 ) resistance.
- FIG. 9 A Schematic of mating-out assay, in which transposition events into the F-plasmid are monitored via drug selection.
- E. coli donor cells carrying an F-plasmid were transformed with a plasmid encoding TnpA and ISG5t2-derived mini-Tn. After induction of T
- FIG. 9C Drug-selected cells from mating-out assays contain TAM-proximal IS insertions, as evidenced by long-read Nanopore sequencing. A genetic map of the F-plasmid is shown, along with the location of distinct ISGrt2-derived mini-Tn integration events. The insets show a zoom-in view of each integration site at the nucleotide level, with the TAM motif highlighted in yellow and the integration site specified by an arrow.
- FIG. 10D DNA cleavage by IscB is highly sensitive to TAM mutations, as assessed by plasmid interference assays. Data are shown as in FIG. 10A, with the indicated TAM sequences; TTCAT denotes the WT TAM, and NT denotes a nontargeting control.
- FIG. 10E TnpB2 is only active for targeted genomic DNA cleavage using select toRNAs, as assessed by genome targeting assays. Transformants with a non-targeting (NT) or one of three ZacZ-specific guides were serially diluted and plated on selective media at 37 °C for 24 h.
- FIGS. 11 A-l ID show off-target ChlP-seq DNA binding analyses.
- FIG. 11 A ChlP-seq experiments reveal recruitment of dlscB to the target site (blue triangle) with a targeting raRNA shown as two independent reps.
- Representative off-target sites for dlscB identified by MACS3 are highlighted (OT1-4) and analyzed in middle and right panels, respectively.
- Middle panel highlights analysis of off-target binding events by dlscB using MEME ChIP, as shown in FIG. 4B.
- Motifs shared by off-target peaks reveal conserved TAM sequences and little conservation of the adjacent seed sequence (left; SEQ ID NOs: 236-240 for On, OT1, OT2, OT3, and OT4, respectively).
- the sequence of the 5’ end of the corresponding coRNA is shown at the bottom of each motif. Two targeting replicates are shown, n indicates the number of peaks contributing to the motif and their percentage of total peaks called by MACS3; E, E-value significance of the motif generated from the MEME ChIP analysis (right of weblogo).
- DNA sequences corresponding to the on-target and off-target sites are shown on right with TAM (yellow) and mismatches (red) highlighted.
- FIG. 1 IB ChlP-seq experiments reveal recruitment of dTnpB2 to the target site (blue triangle) with a targeting raRNA shown as two independent replicates. Data shown as in FIG. 11 A. Similar to dlscB, dTnpB2 shows limited seed sequence requirements. SEQ ID NOs: 241-245 for On, OT1, OT2, OT3, and OT4, respectively.
- FIG. 11C ChlP-seq experiments reveal recruitment of dCas9 to the target site (blue triangle) with a targeting coRNA shown as two independent replicates. Data shown as in FIG HA.
- FIG. 1 ID ChlP-seq experiments reveal recruitment of dCasl2a to the target site (blue triangle) with a targeting coRNA shown as two independent replicates. Data shown as in FIG. 11 A. Analysis of off-target sites reveals a short (4-5 nt) seed sequence adjacent to PAM motif. SEQ ID NOs: 251-255 for On, OT1, OT2, OT3, and OT4, respectively.
- FIGS. 12A-12C show qPCR analysis of IS element loss upon TnpA and TnpB coexpression.
- FIG. 12A Schematic of qPCR-based strategy for quantifying excision. Primers are designed flanking the donor joint following excision and re-ligation. Selective PCR conditions with a shortened extension time allows for reduced amplification of the starting locus containing the mini-Tn.
- FIG. 12B Comparison of simulated excision frequencies, generated by mixing clonally excised and unexcised lysate in known ratios, versus experimentally determined integration efficiencies measured by qPCR.
- FIG. 12C qPCR-based quantification of transposon excision.
- FIG. 13 is a schematic of Clostridium botulinum (Cbo) IStron (CboIStron) and a covariation model of CboTnpB (oRNA. Green rectangle indicates IStron parts derived from group I intron and shows boundaries of mobile genetic element. Covariation model of CboTnpB mRNA is shown in the inset PK1 indicates a possible pseudoknot formation site. Dashed line separating covariation model of mRNA and the guide sequence indicates 3’ IStron boundary.
- FIGS. 14A-14E show CboTnpB robustly cleaves plasmid DN A in E. coli.
- FIG. 14A Schematic of plasmid interference assay in E. coli. Protein-RNA complexes are encoded by pEffector, and targeted cleavage of pTarget results in a loss of kanamycin resistance and cell lethality on selective LB-agar plates.
- FIG. 14B CboTnpB actively cleaves DNA when both TAM and target complementary to mRNA are present
- FIG. 14C CboTnpB DNA cleavage is dependent on RuvC active site.
- FIG. 14A Schematic of plasmid interference assay in E. coli. Protein-RNA complexes are encoded by pEffector, and targeted cleavage of pTarget results in a loss of kanamycin resistance and cell lethality on selective LB-agar plates.
- FIG. 14B CboTnpB
- FIG 14D Mature mRNA species are detected only in the presence of active CboTnpB, the arrow indicates 5’ processing site.
- FIG 14E mRNA maturation site shown on the covariation model, cleavage site indicated by the red arrow.
- FIGS. 15A-15C show unbiased detection of CboTnpB TAM
- FIG. 15 A Schematic of plasmid interference assay in E. coli. pEffector encoded protein-RNA complexes lead to targeted cleavage of pTargets which have a compatible TAM sequence. This results in a loss of kanamycin resistance and cell lethality on selective LB-agar plates.
- FIG. 15B Schematic of the plasmid library targeting. Degenerate 6 nt sequence is located at the 5’ to the guide sequence. Target SEQ ID NOs 256 and 257; Guide SEQ ID NO: 258.
- FIG 15C WebLogo representation of 50 most depleted library members. Consensus motif is located 5' to the target sequence.
- FIGS. 16A-16C show CboIStron actively self-splices in E. coli at the RNA level.
- FIG. 16 A A model of IStron splicing, leading to its removal from transcribed RNA and relegation of exons.
- FIG 16B Schematic of a minimal IStron construct used for splicing assays in E. coli (top row) and the selected truncations to determine predicted right end structure for splicing.
- FIG. 16C RT-PCR gel showing splicing of the minimal IStron and selected right-end truncations.
- FIGS. 16A-16C show CboIStron actively self-splices in E. coli at the RNA level.
- FIG. 16 A A model of IStron splicing, leading to its removal from transcribed RNA and relegation of exons.
- FIG 16B Schematic of a minimal IStron construct used for splicing assays in E. coli (top row) and the
- FIG. 17A-17B show CboTnpA excises the IStron at the DNA level, and the donor junction is recognized by TnpB.
- FIG. 17A A model of IStron mobility mediated by TnpA, showing its excision from native location and integration in a new location. The newly formed donor junction can be recognized by TnpB and either promote recombination of the element back into its previous location or cause the loss of the plasmid due to double-stranded break.
- FIG. 17B Excision assay showing that IStron is effectively excised by TnpA, but that the excision product is undetectable in the presence of TnpB.
- FIG. 18 is graphs of editing outcomes with TnpB and IscB proteins.
- Various TnpB and IscB proteins were analyzed in human cells for their potential editing efficiencies at multiple target sites within the HEK3 locus.
- Each graph reports the DNA editing efficiency for the genome editing reagent shown in the title at the top of the graph; editing efficiencies were calculated as the indel frequency from high-throughput sequencing data, with the aid of CRISPResso2.
- Cas9 is shown as a positive control (upper left).
- “NT’ represents a non-targeting coRNA
- T represents a targeting coRNA.
- T to G represents an coRNA in which the 5’ sequence was extended to the nearest G base, such that the IscB coRNA expresses a completely complementary coRNA while still beginning with a “G” for proper U6-based RNA expression to occur.
- FIGS. 19A-19E show experiments revealing the TnpA activity in stimulating recombination efficiencies.
- FIG. 19A Schematic of experimental workflow to investigate transposon recombination in E. coll in the presence of TnpA and TnpB.
- a native ISGs/2 transposon encoding either TnpB or both TnpA and TnpB was cloned adjacent to a compatible TAM site within plasmid-encoded lacZ, and this plasmid was used to transform E. coll containing an intact lacZ locus.
- FIG. 19B Images of representative LB-agar plates, highlighting the roles of TnpA and TnpB in transposon maintenance and spread via recombination.
- M TnpA (Y125A) mutant; dTnpB, D196A mutant.
- FIG. 19C Transposon-encoded TnpA and TnpB collaborate to efficiently mobilize themselves into a vacant donor site via recombination.
- FIGS. 20A-20D show the genomic architecture and endogenous splicing activity of TnpB-encoding IStrons.
- FIG. 20A IS607-family transposons mobilize through a dsDNA intermediate using a serine-family recombinase (TnpAs, right), in contrast to IS200/IS605-family transposons, which mobilize through a ssDNA intermediate using a tyrosine-family recombinase (TnpAv, left).
- Transposons of both families are bounded by conserved left end (LE) and right end (RE) sequences, encode tnpB accessory genes, excise as circular intermediates, and generate scarless donor joints that precisely regenerate the native genomic sequence.
- FIG. 20A IS607-family transposons mobilize through a dsDNA intermediate using a serine-family recombinase (TnpAs, right), in contrast to IS200/IS605-family transposons, which mobilize through
- FIG. 20B Genetic architecture of representative IS605 and IS607-family IS elements in comparison to closely related IStrons. Both families encode TnpA and TnpB proteins, but element ends are different: IStrons have a notably longer LE where they harbor catalytic core of the intron.
- FIG. 20C Phylogenetic tree of group I introns that are structurally related to the CioIStron group I intron (left), with genetic architectures of select clades schematized (right). The outer rings of the tree indicate associations with TnpAs or TnpAv, as well as whether the group I intron is encoded within an rRNA locus.
- FIG. 20D RNA-seq and whole-genome sequencing (WGS) data from two representative IS607-family transposons in C. senegalense, that encode identifiable group I introns; annotated genes are schematized below the graphs. RNA-seq coverage corresponding to putative toRNAs are labeled, as are the number and connectivity of spliced exon-exon junction reads (orange).
- FIGS. 22A-22F show the genomic and functional analysis of IS200/IS605-family IStrons from C. difficile (CdiTStron).
- FIG 22A transposon left end (LE; SEQ ID NO: 259) and right end (RE, SEQ ID NO: 260) covariance models for CtiiTStron; the predicted LE and RE secondary structures recognized by TnpAy during transposon excision and integration are shown in the inset (top).
- a homologous C. difficile genomic locus lacking the transposon insertion is shown below.
- FIG. 22B DNA multiple sequence alignment of transposon left end (LE, SEQ ID NOs: 261-270) and right end (RE, SEQ ID NOs: 271-280) sequences for 10 select Cc/zIStrons, based on comparative genomics and covariance models, with a consensus sequence shown at the top.
- the transposon adjacent motif (TAM), transposon encoded motif (TEM), and DNA guide sequences for both LE and RE are highlighted in yellow (TAM and LE guide) and orange (TEM and RE guide); dotted black lines indicate the upstream and downstream transposon boundaries.
- FIG. 22C Secondary structure of the group I intron from a representative CdzlStron, with scaffold, substrate, and catalytic domains colored in green, brown, and yellow, respectively.
- Paired stem-loops defined as P1-P9, according to conventions defined by Hasselmayer el al. (Anaerobe. 2004 Apr; 10(2): 85-92); the region that harbors tnpAy and/or tnpB ORFs is indicated, as are the predicted 3' and 5' splice sites (SS).
- FIG. 22D Schematic showing the predicted exonexonjunction products upon self-splicing of two representative CtizIStrons, compared to the coding sequences from otherwise isogenic strains that lack the IStron insertion. Protein sequences SEQ ID NOs: 281-285; DNA sequences SEQ ID NOs: 287-292, top to bottom respectively.
- FIG. 22E Predicted rnRNA secondary structure (SEQ ID NO: 293) for a representative Cdi'IStron, based on secondary structure folding and alignment to the covariance model. The region also recognized by TnpAy at the DNA level is highlighted in orange. A cryoEM structure of DraTnpB (ISDra2) bound to its coRNA substrate (PDB ID: 8BF8) is shown at right, highlighting the stem-loop (orange) that is recognized similarly at the RNA and DNA levels by TnpB and TnpAy, respectively.
- FIG. 22F Secondary structure of the transposon RE ssDNA (SEQ ID NO: 294) for the same CtizIStron from FIG.
- FIG. 23 shows comparative sequence and RNA-seq analyses of C. difficile intron
- FIGS. 24A-24F show the genomic and functional analysis of IS607-family IStrons from C. botulinum (CAoIStron).
- FIG. 24A Schematic of episomal prophage in C. botulinum strain lCbl6868 (NCBI accession ID: NZ CM003334.1), highlighting the location of the botulinum neurotoxin gene and IS605-family, IS607-family elements, and IS607-family IStron elements.
- FIG 24B Transposon left end (LE) and right end (RE) definitions for two representative CAoIStron elements, based on comparative genomics. Homologous C.
- FIG. 24C DNA multiple sequence alignment of transposon LE (SEQ ID NOs: 295-304) and RE (SEQ ID NOs: 305-314) sequences for 10 select C6oIStrons, with a consensus sequence shown at the top.
- the predicted transposon adjacent motif (TAM) is highlighted in yellow; dotted black lines indicate the upstream and downstream transposon boundaries.
- FIGS. 25A-25B show the evolutionary and neighborhood analyses of transposon- associated Arc-like proteins.
- FIG. 25A Phylogenetic tree of Arc-like proteins, revealing genetic associations with TnpB (IS-family transposons) and Casl2k (CRISPR-associated transposons).
- FIG 25B Genetic architecture of representative transposable elements encoding Arc-like proteins (orange arrow), including IStron, IS, and CAST elements. Relevant genes are annotated, and putative transposon boundaries are indicated with inverted green triangles.
- FIGS. 26A-26G show that C6oTnpAs catalyzes efficient IStron excision and integration, with unique dinucleotide requirements.
- FIG. 26A Schematic of transposon excision assay using a CboTnpAs expression plasmid (pTnpAs) and CAoIStron donor plasmid harboring a mini-transposon with LE and RE boundaries (pDonor). Expected substrates and products generated upon transposon excision by PCR are indicated, as are the primer binding sites.
- FIG. 26B Gel electrophoresis (left) and Sanger sequencing (right) of PCR products (SEQ ID NOs: 331-333) from FIG.
- FIGS. 27A-27D show molecular and sequence determinants of CAoIStron DNA excision by C6oTnpAs.
- FIG. 27 A Schematic of transposon excision assay using a CAoTnpAs expression plasmid (pTnpAs) and CAoIStron donor plasmid harboring a mini-transposon with LE and RE boundaries (pDonor). Expected substrates and products generated upon transposon excision are indicated, as are the primer binding sites for quantitative excision measurements using qPCR.
- FIG. 27B Gel electrophoresis (left) and Sanger sequencing (right) of PCR products (SEQ ID NOs: 334-336, respectively) from FIG.
- FIG. 29F Results from a TAM library cleavage assay using a wild-type coRNA, revealing that CAoTnpB requires a consensus 5'-(T)GGG-3' TAM for efficient DNA cleavage. The WebLogo was generated using the 20-most depleted sequences after deep sequencing pTarget from surviving colonies (see Fig. 11 A).
- FIG. 29G Violin plots of TAM enrichment from TAM library assays using variant TnpB-coRNA expression plasmids with the indicated nucleotide in the -1 position of the coRNA.
- FIG. 33C Bacterial spot assays for the same RE/ooRNA deletion constructs in FIG. 33B, in which RNA-guided DNA cleavage leads to cell death.
- TnpB was expressed with either a targeting (T) or non-targeting (NT) coRNA, and transformants were serially diluted, plated on selective media, and cultured at 37 °C for 24 h. Any deletion beyond 180 bp eliminates DNA cleavage activity.
- FIG. 33D RT-qPCR analysis of splicing efficiency (left), and spot assays to monitor RNA-guided DNA cleavage activity (right), for the indicated RE/coRNA pseudo-knot mutations, plotted as in FIGS. 33B and 33C.
- PKMUTI and PKMUT2 contain mutations to either the upstream or downstream motif, whereas PKCOMP contains compensatory mutations in both motifs.
- the results indicate that coRNA PK disruption abrogates TnpB-mediated DNA cleavage, while any mutation to the downstream PK motif abrogates intron splicing; intron splicing is strongly stimulated by mutations to the upstream PK motif.
- FIG. 33E RT-qPCR analysis of splicing efficiency in the presence of a second effector plasmid harboring tnpB, dtnpB, or a codon-optimized (CO) dtnpB gene. Empty refers to an empty vector control.
- FIG. 34B Quantitative measurements of the spliced/unspliced ratio by RT-qPCR for the indicated constructs that harbor deletions in the RE/coRNA region.
- the WT construct contains 221 -bp of the RE, whereas a shorter 20-bp construct exhibits far greater splicing activity. Any deletion beyond 16 bp leads to a loss of splicing activity.
- FIG. 34C Quantitative measurements of the spliced/unspliced ratio by RT-qPCR for the indicated constructs that harbor stem-loop (SL) deletions RE/coRNA region, as defined in FIG. 33A.
- the WT constructs contains 221-bp of the RE.
- the disclosed systems, kits, and methods provide systems and methods for nucleic acid modification.
- each intervening number there between with the same degree of precision is explicitly contemplated.
- the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated.
- nucleic acid refers to a polymer or oligomer of pyrimidine and/or purine bases, preferably cytosine, thymine, and uracil, and adenine and guanine, respectively (See Albert L. Lehninger, Principles of Biochemistry, at 793- 800 (Worth Pub. 1982)).
- the present technology contemplates any deoxyribonucleotide, ribonucleotide, or peptide nucleic acid component, and any chemical variants thereof, such as methylated, hydroxymethylated, or glycosylated forms of these bases, and the like.
- the polymers or oligomers may be heterogenous or homogenous in composition and may be isolated from naturally occurring sources or may be artificially or synthetically produced.
- the nucleic acids may be DNA or RNA, or a mixture thereof, and may exist permanently or transitionally in single-stranded or double-stranded form, including homoduplex, heteroduplex, and hybrid states.
- a nucleic acid or nucleic acid sequence comprises other kinds of nucleic acid structures such as, for instance, a DNA/RNA helix, peptide nucleic acid (PNA), morpholino nucleic acid (see, e.g., Braasch and Corey, Biochemistry, 41(14): 4503-4510 (2002)) and U.S. Pat. No.
- LNA locked nucleic acid
- cyclohexenyl nucleic acids see Wang, J. Am. Chem. Soc., 122: 8595-8602 (2000), and/or a ribozyme.
- nucleic acid or “nucleic acid sequence” may also encompass a chain comprising non-natural nucleotides, modified nucleotides, and/or non- nucleotide building blocks that can exhibit the same function as natural nucleotides (e.g., “nucleotide analogs”); further, the term “nucleic acid sequence” as used herein refers to an oligonucleotide, nucleotide or polynucleotide, and fragments or portions thereof, and to DNA or RNA of genomic or synthetic origin, which may be single or doublestranded, and represent the sense or antisense strand.
- nucleic acid refers to a polymeric form of nucleotides of any length, either deoxyribonucleotides or ribonucleotides, or analogs thereof.
- percent sequence identity refers to the percentage of nucleotides or nucleotide analogs in a nucleic acid sequence, or amino acids in an amino acid sequence, that is identical with the corresponding nucleotides or amino acids in a reference sequence of the present disclosure after aligning the two sequences and introducing gaps, if necessary, to achieve the maximum percent identity.
- a number of mathematical algorithms for obtaining the optimal alignment and calculating identity between two or more sequences are known and incorporated into a number of available software programs.
- Such programs include CLUSTAL-W, T-Coffee, and ALIGN (for alignment of nucleic acid and amino acid sequences), BLAST programs (e.g., BLAST 2.1, BL2SEQ, and later versions thereof) and PASTA programs (e.g., FASTA3x, FASTM, and SSEARCH) (for sequence alignment and sequence similarity searches).
- BLAST programs e.g., BLAST 2.1, BL2SEQ, and later versions thereof
- PASTA programs e.g., FASTA3x, FASTM, and SSEARCH
- Sequence alignment algorithms also are disclosed in, for example, Altschul et al, J. Molecular Biol., 215(3): 403-410 (1990), Beigert et al, Proc. Natl. Acad. Sci.
- hybridization is used in reference to the pairing of complementary nucleic acids. Hybridization and the strength of hybridization (e.g., the strength of the association between the nucleic acids) is influenced by such factors as the degree of complementary between the nucleic acids, stringency of the conditions involved, and the T m of the formed hybrid.
- Hybridization methods involve the annealing of one nucleic acid to another, complementary nucleic acid, e.g., a nucleic acid having a complementary nucleotide sequence.
- a nucleic acid having a complementary nucleotide sequence The ability of two polymers of nucleic acid containing complementary sequences to find each other and “anneal” or “hybridize” through base pairing interaction is a well-recognized phenomenon.
- the initial observations of the “hybridization” process by Marmur and Lane, Proc. Natl. Acad. Set. USA, 46; 453 (1960) and Doty et al, Proc. Natl. Acad. Set. USA, 46; 461 (1960), have been followed by the refinement of this process into an essential tool of modem biology. For example, hybridization and washing conditions are now well known and exemplified in Sambrook et al., supra. The conditions of temperature and ionic strength determine the “stringency” of the hybrid
- Complementarity refers to the ability of a nucleic acid to form hydrogen bond(s) with another nucleic acid sequence by either traditional Watson-Crick or other non-traditional types.
- a percent complementarity indicates the percentage of residues in a nucleic acid molecule, which can form hydrogen bonds (e.g., Watson-Crick base pairing) with a second nucleic acid sequence.
- Full complementarity is not necessarily required, provided there is sufficient complementarity to cause hybridization.
- a “double-stranded nucleic acid” may be a portion of a nucleic acid, a region of a longer nucleic acid, or an entire nucleic acid.
- a “double-stranded nucleic acid” may be, e.g., without limitation, a double-stranded DNA, a double-stranded RNA, a double-stranded DNA/RNA hybrid, etc.
- a single-stranded nucleic acid having secondary structure e.g., basepaired secondary structure
- higher order structure e.g., a stem-loop structure
- triplex structures are considered to be “double-stranded.”
- any base-paired nucleic acid is a “double-stranded nucleic acid.”
- RNA refers to a DNA sequence that comprises control and coding sequences necessary for the production of an RNA having a non-coding function (e.g., a ribosomal or transfer RNA), a polypeptide, or a precursor of any of the foregoing.
- the RNA or polypeptide can be encoded by a full length coding sequence or by any portion of the coding sequence so long as the desired activity or function is retained.
- a “gene” refers to a DNA or RNA, or portion thereof, that encodes a polypeptide or an RNA chain that has functional role to play in an organism.
- genes include regions that regulate the production of the gene product, whether or not such regulatory sequences are adjacent to coding and/or transcribed sequences. Accordingly, a gene includes, but is not necessarily limited to, promoter sequences, terminators, translational regulatory sequences such as ribosome binding sites and internal ribosome entry sites, enhancers, silencers, insulators, boundary elements, replication origins, matrix attachment sites, and locus control regions.
- nucleic acid molecules or polypeptides mean that the nucleic acid molecule or the polypeptide is at least substantially free from at least one other component with which they are naturally associated in nature and as found in nature.
- a “vector” or “expression vector” is a replicon, such as plasmid, phage, virus, or cosmid, to which another DNA segment, e.g., an “insert,” may be attached or incorporated so as to bring about the replication of the attached segment in a cell.
- a cell has been “genetically modified,” “transformed,” or “transfected” by exogenous DNA, e.g., a recombinant expression vector, when such DNA has been introduced inside the cell.
- exogenous DNA e.g., a recombinant expression vector
- the presence of the exogenous DNA results in permanent or transient genetic change.
- the transforming DNA may or may not be integrated (covalently linked) into the genome of the cell.
- the transforming DNA may be maintained on an episomal element such as a plasmid.
- a stably transformed cell is one in which the transforming DNA has become integrated into a chromosome so that it is inherited by daughter cells through chromosome replication.
- a “clone” is a population of cells derived from a single cell or common ancestor by mitosis.
- a “cell line” is a clone of a primary cell that is capable of stable growth in vitro for many generations.
- a “subject” or “patient” may be human or non-human and may include, for example, animal strains or species used as “model systems” for research purposes, such a mouse model as described herein. Likewise, patient may include either adults or juveniles (e.g., children). Moreover, patient may mean any living organism, preferably a mammal (e.g., human or nonhuman) that may benefit from the administration of compositions contemplated herein.
- mammals include, but are not limited to, any member of the Mammalian class: humans, nonhuman primates such as chimpanzees, and other apes and monkey species; farm animals such as cattle, horses, sheep, goats, swine; domestic animals such as rabbits, dogs, and cats; laboratory animals including rodents, such as rats, mice and guinea pigs, and the like.
- nonmammals include, but are not limited to, birds, fish, and the like.
- the mammal is a human.
- contacting refers to bring or put in contact, to be in or come into contact.
- contact* refers to a state or condition of touching or of immediate or local proximity. Contacting a composition to a target destination, such as, but not limited to, an organ, tissue, cell, or tumor, may occur by any means of administration known to the skilled artisan.
- the terms “providing,” “administering,” and “introducing,” are used interchangeably herein and refer to the placement of the systems of the disclosure into a cell, organism, or subject by a method or route which results in at least partial localization of the system to a desired site.
- the systems can be administered by any appropriate route which results in delivery to a desired location in the cell, organism, or subject.
- Transposons encode RNA-guided DNA nucleases that are evolutionary ancestors to CRISPR-Cas9 and Cast 2 enzymes, named IscB and TnpB respectively, but are roughly four times smaller and compact in size. These smaller nucleases function (e.g., in human cells) for targeted DSBs and genome editing. Because of their smaller size, IscB and TnpB nucleases offer promise for next-generation genome editing, since they are within the size range where packaging inside of small viral vectors (like AAV) becomes feasible, for example for use in base editing, prime editing, and epigenome editing. Indeed, IscB and TnpB show promise for a similar range of diverse genome engineering applications as has already been demonstrated with Cas9 and Cas 12, but again, using a smaller and more compact protein-RNA system.
- the systems comprise: a TnpA protein, a TnpB protein, an IscB protein, or a combination thereof, and/or one or more nucleic acids encoding thereof; and optionally, at least one guide RNA, or one or more nucleic acids encoding thereof, complementary to at least a portion of a target nucleic acid.
- the system comprises, consists of, or consists essentially of a
- the system comprises, consists of, or consists essentially of a TnpA protein and at least one guide RNA.
- the system comprises, consists of, or consists essentially of a
- the system comprises, consists of, or consists essentially of a TnpB protein and at least one guide RNA.
- the system comprises a TnpA protein and a DNA nuclease capable of inducing site-specific single or double strand breaks, or one or more nucleic acids encoding thereof.
- the Cas CRISPR/Cas nuclease can be from any Type or Class of CRISPR-Cas systems (e.g., Class 1, Class 3, Types I- VI, or any of subtypes thereof).
- the CRISPR/Cas nuclease is Cas9 or Cas 12.
- the DNA nuclease is an RNA-guided DNA nuclease encoded by insertion sequences.
- the DNA nuclease encoded by insertion sequences is IscB, IsrB, TnpB, or Fanzor.
- the DNA nuclease is a homing endonuclease.
- the homing endonuclease is ISce-I, ICre-I, or HO.
- At least one of the TnpA, TnpB, and IscB proteins is derived from Geobacillus stearothermophilus, Clostridium botulinum, Clostridium senegalense or Clostridioides difficile.
- the TnpA protein may be a serine-family recombinase or, alternatively, a tyrosinefamily recombinase.
- the TnpA protein comprises an amino acid sequence having at least 70% (e.g., having at least 75%, at least 80%, at least 85%, at least 90%, at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identity to any of SEQ ID NO: 11, 21, 25, and 38-41.
- the TnpA protein comprises an amino acid sequence of any of SEQ ID NO: 11, 21, 25, and 38-41.
- the TnpB protein may be derived from an IS607-family or an IS200/IS605-family.
- the TnpB protein comprises an amino acid sequence having at least 70% (e.g., having at least 75%, at least 80%, at least 85%, at least 90%, at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identity to any of SEQ ID NOs: 1-4, 6-9, 17, 22-24, 30-37, and 42-50.
- the TnpB protein comprises an amino acid sequence of any of SEQ ID NO: 1-4, 6-9, 17, 22-24, 30-37, and 42-50.
- the IscB protein comprises an amino acid sequence having at least 70% (e.g., having at least 75%, at least 80%, at least 85%, at least 90%, at least 92%, at least 95%, at least 96%, at least 97%, at least 98%, or at least 99%) identity to SEQ ID NO: 5 or 10. In some embodiments, the IscB protein comprises an amino acid sequence of SEQ ID NO: 5 or 10.
- the TnpA protein may be a serine-family recombinase or a tyrosine-family recombinase.
- TnpA derived from IS607-family transposons represents a serine-family recombinase, hereby indicated by the suffix "(S)" to signify its serine catalytic active site.
- G. stearothermophilus TnpA corresponds to a tyrosine-family recombinase, referenced as TnpA(Y), emphasizing its tyrosine catalytic active site.
- Any of the proteins described or referenced herein may comprise one or more amino acid substitutions as compared to the recited sequences.
- An amino acid “replacement” or “substitution” refers to the replacement of one amino acid at a given position or residue by another amino acid at the same position or residue within a polypeptide sequence.
- Amino acids are broadly grouped as “aromatic” or “aliphatic.” An aromatic amino acid includes an aromatic ring. Examples of “aromatic” amino acids include histidine (H or His), phenylalanine (F or Phe), tyrosine (Y or Tyr), and tryptophan (W or Trp).
- Non-aromatic amino acids are broadly grouped as “aliphatic.”
- “aliphatic” amino acids include glycine (G or Gly), alanine (A or Ala), valine (V or Vai), leucine (L or Leu), isoleucine (I or He), methionine (M or Met), serine (S or Ser), threonine (T or Thr), cysteine (C or Cys), proline (P or Pro), glutamic acid (E or Glu), aspartic acid (A or Asp), asparagine (N or Asn), glutamine (Q or Gin), lysine (K or Lys), and arginine (R or Arg).
- the amino acid replacement or substitution can be conservative, semi-conservative, or non-conservative.
- the phrase “conservative amino acid substitution” or “conservative mutation” refers to the replacement of one amino acid by another amino acid with a common property.
- a functional way to define common properties between individual amino acids is to analyze the normalized frequencies of amino acid changes between corresponding proteins of homologous organisms (Schulz and Schirmer, Principles of Protein Structure, Springer-Verlag, New York (1979)). According to such analyses, groups of amino acids may be defined where amino acids within a group exchange preferentially with each other, and therefore resemble each other most in their impact on the overall protein structure (Schulz and Schirmer, supra).
- conservative amino acid substitutions include substitutions of amino acids within the sub-groups described above, for example, lysine for arginine and vice versa such that a positive charge may be maintained, glutamic acid for aspartic acid and vice versa such that a negative charge may be maintained, serine for threonine such that a free -OH can be maintained, and glutamine for asparagine such that a free -NHz can be maintained.
- “Semi-conservative mutations” include amino acid substitutions of amino acids within the same groups listed above, but not within the same sub-group. For example, the substitution of aspartic acid for asparagine, or asparagine for lysine, involves amino acids within the same group, but different sub-groups.
- “Non-conservative mutations” involve amino acid substitutions between different groups, for example, lysine for tryptophan, or phenylalanine for serine, etc.
- the TnpA, TnpB, and or IscB protein may be fully or partially catalytically inactivated by one or more amino acid substitutions.
- Fully or partially catalytically inactivated variants of the proteins as disclosed herein may still function as a nucleic acid binding protein, alone or in coordination with a guide RNA or other protein, with the targeting capabilities of the fully functioning protein.
- any of the proteins disclosed herein may further comprise one or more proteins, polypeptides (e.g., protein domain sequences), or peptides fused to the polypeptide.
- the proteins disclosed herein may be fused to another protein or protein domain that provides for tagging or visualization (e.g., GFP).
- the one or more proteins, polypeptides (e.g., protein domain sequences), or peptides may be appended at an N -terminus, a C-terminus, internally, or a combination thereof.
- the one or more proteins, polypeptides (e.g., protein domain sequences), or peptides may be fused in any orientation in relationship to the disclosed protein.
- effector polypeptides include proteins or protein domains that have additional functionality or activity useful to target to certain DNA sequences.
- the effector polypeptide may comprise a number of functionalities, including but not limited to, nuclease function, recombinase function, epigenetic modifying function, transposase function, integrase function, resolvase function, invertase function, protease function, DNA methyltransferase function, DNA demethylase function, histone acetylase function, histone deacetylase function, transcriptional repressor function, transcriptional activator function, DNA binding protein function, transcription factor recruiting protein function, nuclear-localization signal function, DNA editing function (e.g., deaminase) or any combination thereof.
- some effector domains function in transcriptional regulation via their ability to interact with the basal transcriptional machinery and general co-activators, interact with
- the system described herein is used to modulate gene regulatory activity, such as transcriptional or translational activity.
- the at least one effector polypeptide may comprise activator and/or repressor activity that can affect transcription upstream and downstream of coding regions, and can be used to activate or repress gene expression.
- the at least one effector polypeptide may include domains from transcription factors (activators, repressors, coactivators, co-repressors), silencers, and/or chromatin associated proteins and their modifiers (e.g., methylases, demethylases, acetylases and deacetylases).
- a system as disclosed herein having a transcription activator effector polypeptide can be used to directly increase gene expression.
- a system as disclosed herein comprising a transcriptional protein recruiting domain, or active fragment thereof can be used to recruit transcriptional activators or repressors to a specific nucleic acid sequence to localize activators and repressors to modulate gene expression in a targeted manner.
- the effector polypeptide comprises transcriptional repressor function. Transcription repressors prevent, partially or completely, the transcription of genes near to their target site.
- Exemplary transcriptional repressors include, but are not limited to, KRAB-domain containing proteins, SID, and Spl.
- the effector polypeptide comprises transcriptional activator function.
- Transcriptional activators can be generally defined as proteins, or domains thereof, that bind to specific sites on promoter DNA and bring about increased transcription of specific genes through interactions with other proteins.
- Exemplary transcriptional activators include, but are not limited to, VP64, p65, p53, c-Myb, GATA-1, EKLF, MyoD, E2F, dTCF, Tat, HSF1, RTA and SET7/9.
- the effector polypeptide comprises DNA methyltransferase or DNA methylase function.
- DNA methyltransferases are a family of DNA modifying proteins composed of different isomers (e.g., DNMT1, DNMT3A, and DNMT3B).
- Other exemplary DNA methyltransferases include Sssl methylase, Alul methylase, Haelll methylase, Hhal methylase, and Hpall methylase.
- Their main mechanism of action is addition of a methyl group to the fifth carbon of a cytosine residue (5mc) located adjacent to a guanine residue.
- the effector polypeptide comprises DNA demethylase function.
- DNA demethylation can be mediated by at least three enzyme families: (i) the ten-eleven translocation (TET) family, mediating the conversion of 5mC into 5hmC; (ii) the AID/APOBEC family, acting as mediators of 5mC or 5hmC deamination; and (iii) the BER (base excision repair) glycosylase family involved in DNA repair.
- TET ten-eleven translocation
- AID/APOBEC acting as mediators of 5mC or 5hmC deamination
- BER base excision repair glycosylase family involved in DNA repair.
- Kinases, phosphatases, and other proteins that modify or regulate other polypeptides involved in gene regulation are also useful as effector polypeptides. Such modifiers are often involved in switching on or off transcription mediated by, for example, hormones.
- Other useful domains for regulating gene expression can also be obtained from the gene products of oncogenes (e.g., myc, jun, fos, myb, max, mad, rel, ets, bcl, myb, mos family members) and their associated factors and modifiers.
- the effector polypeptide can be used to target enzymatic activity to locations containing the target nucleic acid sequence to which the gRNA is directed.
- effector polypeptides having integrase or transposase activity can be used to promote integration of exogenous nucleic acid sequence into specific nucleic acid sequence regions and/or eliminate (knock-out) specific endogenous nucleic acid sequence.
- Integrases allow for the insertion of nucleic acids, for example, into a host genome
- Integrases are found in a retrovirus such as HIV (human immunodeficiency virus) and lambda integrase.
- the effector polypeptide comprises transposase functionality.
- Transposases are enzymes that bind to the end of a transposon and catalyze its movement by a cut and paste mechanism or a replicative transposition mechanism.
- Exemplary transpoases include, but are not limited to, Tel transposase, Mosl transposase, Tn5 transposase, and Mu transposase
- the effector polypeptide modifies epigenetic signals and thereby modifies gene regulation, for example by promoting histone acetylase and histone deacetylase activity.
- epigenetic modifier refers to a protein or catalytic domain thereof having enzymatic activity that results in the epigenetic modification of DNA, for example, chromosomal DNA.
- Epigenetic modifications include, but are not limited to, histone modifications including methylation and demethylation (e.g., mono-, di- and trimethylation), histone acetylation and deacetylation, as well as histone ubiquitylation, phosphorylation, and sumoylation.
- Histone acetylation and deacetylation are the processes by which the lysine residues within the N-terminal tail protruding from the histone core of the nucleosome are acetylated and deacetylated as part of gene regulation. These reactions are typically catalyzed by enzymes with histone acetyltransferase (HAT) or histone deacetylase (HDAC) activity.
- HAT histone acetyltransferase
- HDAC histone deacetylase
- Histone acetyltransferases include GNAT family proteins (e.g., Gcn5, Gcn5L, p300/CREB-binding protein associated factor (PCAF), Elp3, HPA2 and HAT1) and MYST family proteins (e.g., Sas3, essential SAS-related acetyltransferase (Esal), Sas2, Tip60, MOF, MOZ, MORE, and HBO1).
- GNAT family proteins e.g., Gcn5, Gcn5L, p300/CREB-binding protein associated factor (PCAF), Elp3, HPA2 and HAT1
- MYST family proteins e.g., Sas3, essential SAS-related acetyltransferase (Esal), Sas2, Tip60, MOF, MOZ, MORE, and HBO1.
- Histone deacetylases fall into four classes. Class I includes HDACs 1, 2, 3, and 8. Class II is divided into two subgroups, Class IIA and Class IIB
- Class Ill contains the Sirtuins and Class IV contains only HDAC11.
- Classes of HD AC proteins are divided and grouped together based on the comparison to the sequence homologies of Rpd3, Hosl and Hos2 for Class I HDACs, HDA1 and Hos3 for the Class II HDACs and the sirtuins for Class III HDACs.
- methyltransferases and demethylases, respectively.
- Histone methylases transfer methyl groups to amino acids (e.g., lysine and arginine) of histone proteins, ultimately effecting transcription of genes.
- Methylases include SET1, MLL, SMYD3, G9a, GLP, EZH2, and SETDB1.
- Histone demethylases catalyze the removal of methyl marks from histones, an activity associated with transcriptional regulation and DNA damage repair.
- Demethylases include, for example, KDM1A, KDM1B, KDM2A, KDM2B, UTX,UTY, Jumonji C (JmJC) domaincontaining demethylases, and GSK-J4.
- the effector polypeptide comprises nuclease activity.
- a nuclease is an agent that induces a break in a nucleic acid sequence, e.g., a single or a double strand break in a double-stranded DNA sequence.
- Nucleases include those which cut at or near a preselected or specific sequence and those which are not site specific.
- nucleases include, but are not limited to, zinc finger nucleases (ZFN), homing endonucleases, meganucleases, restriction enzymes, TAL effector nucleases, Argonaute nucleases, CRISPR nucleases, comprising, for example, Cas9, Cpfl, Csml, CasX or CasY nucleases, micrococcal nuclease, staphylococcal nuclease, DNase I, T7 endonuclease, or catalytically active fragments thereof.
- ZFN zinc finger nucleases
- homing endonucleases homing endonucleases
- meganucleases restriction enzymes
- TAL effector nucleases Argonaute nucleases
- CRISPR nucleases comprising, for example, Cas9, Cpfl, Csml, CasX or CasY nucleases, micrococcal nuclease, staphy
- the effector polypeptide comprises invertase activity.
- Invertase activity can be used to alter genome structure by swapping the orientation of a DNA fragment.
- the effector polypeptide comprises recombinase activity.
- a recombinase is a site-specific enzyme that mediates the recombination of DNA between recombinase recognition sequences, which results in the excision, integration, inversion, or exchange (e.g., translocation) of DNA fragments between the recombinase recognition sequences.
- Recombinases can be classified into two distinct families: serine recombinases (e.g., resolvases and invertases) and tyrosine recombinases (e.g., integrases).
- serine recombinases include, without limitation, Hin, Gin, Tn3 (also known as TnpR), (3-six, CinH, ParA, y5, Bxbl, ⁇
- tyrosine recombinases examples include, without limitation, Cre, FLP, R, Lambda, HK101, HK022, and pSAM2.
- the serine and tyrosine recombinase names stem from the conserved nucleophilic amino acid residue that the recombinase uses to attack the DNA and which becomes covalently linked to the DNA during strand exchange.
- the effector polypeptide comprises resolvase activity.
- Resolvases are site-specific recombinases that function to excise (as a circle) a segment of DNA contained between two recombination sites (called res) and include, for example, Ruv C resolvase, Holiday junction resolvase Hjc ,Tn3 and yd resolvase.
- the effector polypeptide comprises a peptide or polypeptide sequence responsive to a ligand, such as a hormone receptor ligand binding domain, including, for example, the ligand binding domains of the estrogen receptor, , the glucocorticosteroid receptor, and the like.
- a ligand such as a hormone receptor ligand binding domain, including, for example, the ligand binding domains of the estrogen receptor, , the glucocorticosteroid receptor, and the like.
- Such effector domains can be used to act as “gene switches,” and be regulated by inducers, such as small molecule or protein ligands, specific for the ligand binding domain.
- the effector polypeptide comprises sequences or domains of polypeptides that mediate direct or indirect protein-protein interactions, including, for example, a leucine zipper domain, a STAT protein N terminal domain, and/or an FK506 binding protein.
- the effector polypeptide comprises DNA editing function (e.g. , deaminase, DNA repair activity, DNA damage activity, dismutase activity, alkylation activity, depurination activity, oxidation activity, pyrimidine dimer forming activity, polymerase activity (e.g., reverse transcriptase), ligase activity, helicase activity, photolyase activity or glycosylase activity).
- DNA editing function e.g. , deaminase, DNA repair activity, DNA damage activity, dismutase activity, alkylation activity, depurination activity, oxidation activity, pyrimidine dimer forming activity
- polymerase activity e.g., reverse transcriptase
- ligase activity e.g., helicase activity
- photolyase activity or glycosylase activity e.g., glycosylase activity
- the effector polypeptide comprises a deaminase, or functional fragment thereof.
- the deaminase, or functional fragment thereof may be derived from a naturally occurring deaminase or variant thereof (e.g., a protein, enzyme, or domain with an amino acid sequence having at least 70% identity to a naturally occurring deaminase).
- the deaminase may be a synthetic or engineered deaminase.
- the deaminase, or functional fragment thereof is an adenosine deaminase, also sometimes referred to as an adenine deaminase.
- the activity mediated by the effector polypeptide is a non- biological activity, such as a fluorescence activity (e.g., fluorescent proteins), luminescence activity (e.g., a luminescent protein or enzyme which results in luminescence when interacting with a substrate (e.g., luciferase)), or binding activity, such as those mediated by maltose binding protein (“MBP’), glutathione S transferase (GST), hexahistidine, c-myc, and the FLAG epitope, for facilitating detection, purification, monitoring expression, and/or monitoring cellular and subcellular localization of the polypeptide to which the effector domain is appended.
- the systems can also be used as a diagnostic reagent, for example, to detect mutations in gene sequences, to purify restriction fragments from a solution, or to visualize DNA fragments of a gel.
- effector polypeptides described herein are illustrative and merely provide the skilled artisan with examples of effectors that can be used in combination with the systems and methods described herein.
- the effector polypeptide comprise fragments of proteins that have been separated from their natural DNA binding domains and engineered to be part of a fusion protein with the protein described herein.
- the effector polypeptides are proteins which normally bind to other proteins or factors which result in their recruitment to a specific or non-specific nucleic acid.
- any of the proteins described or referenced herein may further have a nuclear localization sequence (NLS).
- the at least one nuclear localization sequence may be appended to the N-terminus, the C-terminus, or embedded in the protein (e.g., inserted internally within the open reading frame (ORF)).
- the polypeptides may comprise one or more nuclear localization sequences.
- the nuclear localization sequence may comprise any amino acid sequence known in the art to functionally tag or direct a protein for import into a cell’s nucleus (e.g., for nuclear transport).
- a nuclear localization sequence comprises one or more positively charged amino acids, such as lysine and arginine.
- the NLS is a monopartite sequence.
- a monopartite NLS comprises a single cluster of positively charged or basic amino acids.
- the monopartite NLS comprises a sequence of K-K/R-X-K/R, wherein X can be any amino acid.
- Exemplary monopartite NLSs include, without limitation, those from the SV40 large T-antigen (PKKKRKVEDP; SEQ ID NO: 349), c-Myc (PAAKRVKLD; SEQ ID NO: 350), and TUS- proteins (Kaczmarczyk SJ et al. PLoS ONE 5(1): e8889.2010).
- the NLS comprises a c-Myc NLS.
- the NLS is a bipartite sequence.
- Bipartite NLSs comprise two clusters of basic amino acids, separated by a spacer of about 9-12 amino acids.
- Exemplary bipartite NLSs include the NLS of nucleoplasmin, (SEQ ID NO: 351), the NLS of EGL-13, MSRRRKANPTKLSENAKKLAKEVEN (SEQ ID NO: 352), the bipartite SV40 NLS, (SEQ ID NO: 353).
- the epitope tags may be at the N- terminus, a C-terminus, or a combination thereof of the corresponding protein. In some embodiments, the epitope tag may be adjacent, either upstream or downstream, to a nuclear localization sequence.
- the effector polypeptide, NLS, or epitope tag may be appended to the proteins described herein by a linker.
- the linker may have any of a variety of amino acid sequences. Suitable linkers include polypeptides of between 1 amino acids and 100 amino acids in length, between 4 amino acids and 40 amino acids in length, or between 4 amino acids and 25 amino acids in length. These linkers can be produced by using synthetic, linker-encoding oligonucleotides to couple the proteins, or can be encoded by a nucleic acid sequence encoding the protein. Peptide linkers with a degree of flexibility can be used.
- the systems further comprise a guide RNA complementary to at least a portion of the target nucleic acid sequence, or a nucleic acid encoding the at least one gRNA.
- the gRNA may also comprise a scaffold sequence.
- the gRNA or portion thereof that hybridizes to the target nucleic acid (a target site) may be any length.
- the gRNA sequence that hybridizes to the target nucleic acid is 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 nucleotides in length.
- gRNAs or sgRNA(s) used in the present disclosure can be between about 5 and 100 nucleotides long, or longer (e.g., 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42,
- the gRNA sequence is at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, or at least 100% complementary to a target nucleic acid.
- sgRNA(s) there are many publicly available software tools that can be used to facilitate the design of sgRNA(s); including but not limited to, Genscript Interactive CRISPR gRNA Design Tool, WU-CRISPR, and Broad Institute GPP sgRNA Designer.
- Genscript Interactive CRISPR gRNA Design Tool WU-CRISPR
- WU-CRISPR WU-CRISPR
- Broad Institute GPP sgRNA Designer There are also publicly available pre-designed gRNA sequences to target many genes and locations within the genomes of many species (human, mouse, rat, zebrafish, C. elegant), including but not limited to, IDT DNA Predesigned Alt-R CRISPR-Cas9 guide RNAs, Addgene Validated gRNA Target Sequences, and GenScript Genome-wide gRNA databases.
- the gRNA sequence does not comprise a scaffold sequence and a scaffold sequence is expressed as a separate transcript.
- the gRNA sequence further comprises an additional sequence that is complementary to a portion of the scaffold sequence and functions to bind (hybridize) the scaffold sequence.
- the gRNA and scaffold sequence may be provided as omega RNA (coRNA).
- OJRNAS are provided in the Tables herein, for example, SEQ ID NOs: 12-16, 19-20, 26-29, and 51-57.
- the gRNA may be a non-naturally occurring gRNA.
- the system may further comprise a target nucleic acid.
- target sequence The terms “target sequence,”
- a target sequence may comprise any polynucleotide, such as DNA or RNA.
- Suitable DNA/RNA binding conditions include physiological conditions normally present in a cell.
- Other suitable DNA/RNA binding conditions e.g., conditions in a cell-free system are known in the art.
- the target nucleic acid may or may not be flanked by a transposon adjacent motif (TAM).
- a TAM can be upstream of the target sequence. In one embodiment, the target sequence is immediately flanked on the 5’end by a TAM sequence.
- a TAM can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more nucleotides in length. In certain embodiments, a TAM is between 2-6 nucleotides in length.
- the TAM comprises a sequence of TT(C/T)A(A/T/C).
- the TAM sequence is TTTAT or TTCAT.
- the TAM sequence comprises TGG. Exemplary TAM sequences are provided in the Examples herein. There may be mismatches distal from the TAM
- the target nucleic acid may or may not be flanked by a transposon-encoded motif (TEM) sequence
- TEM transposon-encoded motif
- a TEM can be downstream of the target sequence.
- Exemplary TEM sequences are provided in the Examples herein.
- the target nucleic acid may be flanked by at least one end sequence.
- the system may further include a donor nucleic acid.
- the donor nucleic acid may be a part of a bacterial plasmid, bacteriophage, a virus, autonomously replicating extra chromosomal DNA element, linear plasmid, linear DNA, linear covalently closed DNA, mitochondrial or other organellar DNA, chromosomal DNA, and the like.
- the donor nucleic acid comprises a cargo nucleic acid sequence.
- the donor nucleic acid may be flanked by at least one end sequence.
- the donor nucleic acid is flanked on the 5* and the 3’ end with an end sequence, e.g., at least one of a left end sequence and a right end sequence.
- end sequence refers to any nucleic acid comprising a sequence capable of designating the nucleic acid between the two ends for rearrangement. Usually, these sequences contain inverted repeats and may be about 10-150 base pairs long, however the exact sequence requirements differ for the specific elements and enzymes, as demonstrated in the Examples below. End sequences may or may not include additional sequences that promotes or augment transposition.
- the end sequences on either end may be the same or different.
- the end sequence may be the endogenous end sequences or may include deletions, substitutions, or insertions.
- the endogenous end sequences may be truncated. For example, for Clostridium botulinum the minimal end sequences for a variety of functions are shown in Table 6.
- the donor nucleic acid, and by extension the cargo nucleic acid may of any suitable length, including, for example, about 50-100 bp (base pairs), about 100-1000 bp, at least or about 10 bp, at least or about 20 bp, at least or about 25 bp, at least or about 30 bp, at least or about 35 bp, at least or about 40 bp, at least or about 45 bp, at least or about 50 bp, at least or about 55 bp, at least or about 60 bp, at least or about 65 bp, at least or about 70 bp, at least or about 75 bp, at least or about 80 bp, at least or about 85 bp, at least or about 90 bp, at least or about 95 bp, at least or about 100 bp, at least or about 200 bp, at least or about 300 bp, at least or about 400 bp, at least or about 500 bp, at least or about 600 .
- the system may be a cell free system. Also disclosed is a cell comprising the system described herein.
- the cell is a prokaryotic cell.
- the cell is a eukaryotic cell.
- the cell is a mammalian cell (e.g., a cell of a nonhuman primate or a human cell).
- a eukaryotic cell e.g., a mammalian cell, a human cell.
- the one or more nucleic acids encoding a TnpA protein, a TnpB protein, an IscB protein and guide RNA may be any nucleic acid including DNA, RNA, or combinations thereof.
- nucleic acids comprise one or more messenger RNAs, one or more vectors, or any combination thereof.
- the TnpA protein, TnpB protein and/or IscB protein and the guide RNA are all encoded on the same nucleic acid.
- each of the TnpA protein, TnpB protein, IscB protein and the guide RNA are encoded on different nucleic acids.
- two or more nucleic acids encode any combination of the TnpA protein, TnpB protein and/or IscB protein and the guide RNA (e.g., coRNA) in the system.
- engineering the system for use in eukaryotic cells may involve codon-optimization. It will be appreciated that changing native codons to those most frequently used in mammals allows for maximum expression of the system proteins in mammalian cells (e.g., human cells). Such modified nucleic acid sequences are commonly described in the art as “codon-optimized,” or as utilizing “mammalian-preferred” or “humanpreferred” codons.
- the nucleic acid sequence is considered codon- optimized if at least about 60% (e.g., about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, or about 98%) of the codons encoded therein are mammalian preferred codons.
- the present disclosure also provides for DNA segments encoding the proteins and nucleic acids disclosed herein, vectors containing these segments and cells containing the vectors.
- the vectors may be used to propagate the segment in an appropriate cell and/or to allow expression from the segment (e.g., an expression vector).
- an expression vector The person of ordinary skill in the art would be aware of the various vectors available for propagation and expression of a nucleic acid sequence.
- the present disclosure further provides engineered, non-naturally occurring vectors and vector systems, which can encode one or more or all of the components of the present system.
- the vector(s) can be introduced into a cell that is capable of expressing the polypeptide encoded thereby, including any suitable prokaryotic or eukaryotic cell.
- the vectors of the present disclosure may be delivered to a eukaryotic cell in a subject
- Modification of the eukaryotic cells via the present system can take place in a cell culture, where the method comprises isolating the eukaryotic cell from a subject prior to the modification.
- the method further comprises returning said eukaryotic cell and/or cells derived therefrom to the subject.
- Non-viral vector delivery systems include DNA plasmids, cosmids, RNA (e.g., a transcript of a vector described herein), a nucleic acid, and a nucleic acid complexed with a delivery vehicle.
- Viral vector delivery systems include DNA and RNA viruses, which have either episomal or integrated genomes after delivery to the cell.
- Viral vectors include, for example, retroviral, lentiviral, adenoviral, adeno-associated and herpes simplex viral vectors.
- plasmids that are non-replicative, or plasmids that can be cured by high temperature may be used, such that any or all of the necessary components of the system may be removed from the cells under certain conditions. For example, this may allow for DNA integration by transforming bacteria of interest, but then being left with engineered strains that have no memory of the plasmids or vectors used for the integration.
- Drug selection strategies may be adopted for positively selecting for cells that underwent DNA integration.
- a donor nucleic acid may contain one or more drug-selectable markers within the cargo. Then presuming that the original donor plasmid is removed, drug selection may be used to enrich for integrated clones. Colony screenings may be used to isolate clonal events.
- a variety of viral constructs may be used to deliver the present system or components thereof (such as a TnpA protein, a TnpB protein, an IscB protein, and/or a guide RNA) to the targeted cells and/or a subject
- recombinant viruses include recombinant adeno-associated virus (AAV), recombinant adenoviruses, recombinant lentiviruses, recombinant retroviruses, recombinant herpes simplex viruses, recombinant poxviruses, phages, etc.
- AAV adeno-associated virus
- the present disclosure provides vectors capable of integration in the host genome, such as retrovirus or lentivirus.
- a DNA segment encoding a TnpA protein, a TnpB protein, an IscB protein, and/or a guide RNA is contained in a plasmid vector that allows expression of the protein(s) and subsequent isolation and purification produced by the recombinant vector. Accordingly, the proteins disclosed herein can be purified following expression, obtained by chemical synthesis, or obtained by recombinant methods.
- expression vectors for stable or transient expression may be constructed via conventional methods as described herein and introduced into cells.
- nucleic acids encoding the components of the present system may be cloned into a suitable expression vector, such as a plasmid or a viral vector in operable linkage to a suitable promoter.
- a suitable expression vector such as a plasmid or a viral vector in operable linkage to a suitable promoter.
- the selection of expression vectors/plasmids/viral vectors should be suitable for integration and replication in eukaryotic cells.
- vectors of the present disclosure can drive the expression of one or more sequences in prokaryotic cells.
- Promoters that may be used include T7 RNA polymerase promoters, constitutive E. coli promoters, and promoters that could be broadly recognized by transcriptional machinery in a wide range of bacterial organisms.
- the system may be used with various bacterial hosts.
- vectors of the present disclosure can drive the expression of one or more sequences in mammalian cells using a mammalian expression vector.
- mammalian expression vectors include pCDMS (Seed, Nature (1987) 329:840, incorporated herein by reference) and pMT2PC (Kaufman, et al., EMBO J. (1987) 6:187, incorporated herein by reference).
- the expression vector's control functions are typically provided by one or more regulatory elements.
- commonly used promoters are derived from polyoma, adenovirus 2, cytomegalovirus, simian virus 40, and others disclosed herein and known in the art.
- Vectors of the present disclosure can comprise any of a number of promoters known to the art, wherein the promoter is constitutive, regulatable or inducible, cell type specific, tissuespecific, or species specific.
- a promoter sequence of the invention can also include sequences of other regulatoiy elements that are involved in modulating transcription (e.g., enhancers, Kozak sequences and introns).
- promoter/regulatoiy sequences useful for driving constitutive expression of a gene include, but are not limited to, for example, CMV (cytomegalovirus promoter), EFla (human elongation factor 1 alpha promoter), SV40 (simian vacuolating virus 40 promoter), PGK (mammalian phosphoglycerate kinase promoter), Ubc (human ubiquitin C promoter), human beta-actin promoter, rodent beta-actin promoter, CBh (chicken beta-actin promoter), CAG (hybrid promoter contains CMV enhancer, chicken beta actin promoter, and rabbit betaglobin splice acceptor), TRE (Tetracycline response element promoter), Hl (human polymerase Ill RNA promoter), U6 (human U6 small nuclear promoter), and the like.
- CMV cytomegalovirus promoter
- EFla human elongation factor 1 alpha promoter
- SV40 simi
- Additional promoters that can be used for expression of the components of the present system, include, without limitation, cytomegalovirus (CMV) intermediate early promoter, a viral LTR such as the Rous sarcoma virus LTR, HLV-LTR, HTLV-1 LTR, Maloney murine leukemia virus (MMLV) LTR, myeoloproliferative sarcoma virus (MPSV) LTR, spleen focus-forming virus (SFFV) LTR, the simian virus 40 (SV40) early promoter, herpes simplex tk virus promoter, elongation factor 1- alpha (EFl -a) promoter with or without the EFl -a intron.
- Additional promoters include any constitutively active promoter. Alternatively, any regulatable promoter may be used, such that its expression can be modulated within a cell.
- tissue specific or inducible promoter/regulatory sequences which are useful for this purpose include, but are not limited to, the rhodopsin promoter, the MMTV LTR inducible promoter, the SV40 late enhancer/promoter, synapsin 1 promoter, ET hepatocyte promoter, GS glutamine synthase promoter and many others.
- promoters which are well known in the art can be induced in response to inducing agents such as metals, glucocorticoids, tetracycline, hormones, and the like, are also contemplated for use with the invention.
- promoters which are well known in the art can be induced in response to inducing agents such as metals, glucocorticoids, tetracycline, hormones, and the like, are also contemplated for use with the invention.
- promoters which are well known in the art can be induced in response to inducing agents such as metals, glucocorticoids, tetracycline, hormones, and the like, are also contemplated for use with the invention.
- promoters which are well known in the art can be induced in response to inducing agents such as metals, glucocorticoids, tetracycline, hormones, and the like, are also contemplated for use with the invention.
- promoter/regulatory sequence known in the art that is capable
- the vectors of the present disclosure may direct expression of the nucleic acid in a particular cell type (e.g., tissue-specific regulatory elements are used to express the nucleic acid).
- tissue-specific regulatory elements include promoters that may be tissue specific or cell specific.
- tissue specific refers to a promoter that is capable of directing selective expression of a nucleotide sequence of interest to a specific type of tissue (e.g., seeds) in the relative absence of expression of the same nucleotide sequence of interest in a different type of tissue.
- cell type specific refers to a promoter that is capable of directing selective expression of a nucleotide sequence of interest in a specific type of cell in the relative absence of expression of the same nucleotide sequence of interest in a different type of cell within the same tissue.
- the term “cell type specific” when applied to a promoter also means a promoter capable of promoting selective expression of a nucleotide sequence of interest in a region within a single tissue. Cell type specificity of a promoter may be assessed using methods well known in the art, e.g., immunohistochemical staining.
- the vector may contain, for example, some or all of the following: a selectable marker gene, such as the neomycin gene for selection of stable or transient transfectants in host cells; enhancer/promoter sequences from the immediate early gene of human CMV for high levels of transcription; transcription termination and RNA processing signals from SV40 for mRNA stability; 5 ’-and 3 ’-untranslated regions for mRNA stability and translation efficiency from highly-expressed genes like a-globin or P-globin; SV40 polyoma origins of replication and ColEl for proper episomal replication; internal ribosome binding sites (IRESes), versatile multiple cloning sites; T7 and SP6 RNA promoters for in vitro transcription of sense and antisense RNA; a “suicide switch” or “suicide gene” which when triggered causes cells carrying the vector to die (e.g., HSV thymidine kinase, an inducible caspase such as iCas
- Suitable vectors and methods for producing vectors containing transgenes are well known and available in the art.
- Selectable markers also include chloramphenicol resistance, tetracycline resistance, spectinomycin resistance, streptomycin resistance, erythromycin resistance, rifampicin resistance, bleomycin resistance, thermally adapted kanamycin resistance, gentamycin resistance, hygromycin resistance, trimethoprim resistance, dihydrofolate reductase (DHFR), GPT; the URA3, HIS4, LEU2, and TRP1 genes of S. cerevisiae.
- the vectors When introduced into the cell, the vectors may be maintained as an autonomously replicating sequence or extrachromosomal element or may be integrated into host DNA.
- the present disclosure comprises integration of exogenous DNA into an endogenous gene.
- an exogenous DNA is not integrated into the endogenous gene.
- the DNA may be packaged into an extrachromosomal or episomal vector (such as AAV vector), which persists in the nucleus in an extrachromosomal state, and offers donor-template delivery and expression without integration into the host genome.
- extrachromosomal gene vector technologies has been discussed in detail by Wade-Martins R (Methods Mol Biol. 2011; 738: 1-17, incorporated herein by reference).
- the present system may be delivered by any suitable means.
- the system is delivered in vivo.
- the system is delivered to isolated/cultured cells (e.g., autologous iPS cells) in vitro to provide modified cells usefill for in vivo delivery to patients afflicted with a disease or condition.
- Transfection refers to the taking up of a vector by a cell whether or not any coding sequences are in fact expressed.
- Numerous methods of transfection are known to the ordinarily skilled artisan, for example, lipofectamine, calcium phosphate co-precipitation, electroporation, DEAE-dextran treatment, microinjection, viral infection, and other methods known in the art
- Transduction refers to entry of a virus into the cell and expression (e.g., transcription and/or translation) of sequences delivered by the viral vector genome.
- “transduction” generally refers to entry of the recombinant viral vector into the cell and expression of a nucleic acid of interest delivered by the vector genome.
- any of the vectors comprising a nucleic acid sequence that encodes the components of the present system is also within the scope of the present disclosure.
- a vector may be delivered into host cells by a suitable method.
- Methods of delivering vectors to cells are well known in the art and may include DNA or RNA electroporation, transfection reagents such as liposomes or nanoparticles to delivery DNA or RNA; delivery of DNA, RNA, or protein by mechanical deformation (see, e.g., Sharei et al. Proc. Natl. Acad. Sci. USA (2013) 110(6): 2082- 2087, incorporated herein by reference); or viral transduction.
- the vectors are delivered to host cells by viral transduction.
- Nucleic acids can be delivered as part of a larger construct, such as a plasmid or viral vector, or directly, e.g., by electroporation, lipid vesicles, viral transporters, microinjection, and biolistics (high-speed particle bombardment).
- the construct containing the one or more transgenes can be delivered by any method appropriate for introducing nucleic acids into a cell.
- the construct or the nucleic acid encoding the components of the present system is a DNA molecule.
- the nucleic acid encoding the components of the present system is a DNA vector and may be electroporated to cells.
- the nucleic acid encoding the components of the present system is an RNA molecule, which may be electroporated to cells.
- delivery vehicles such as nanoparticle- and lipid-based mRNA or protein delivery systems can be used.
- Further examples of delivery vehicles include lentiviral vectors, ribonucleoprotein (RNP) complexes, lipid-based delivery system, gene gun, hydrodynamic, electroporation or nucleofection microinjection, and biolistics.
- RNP ribonucleoprotein
- lipid-based delivery system lipid-based delivery system
- gene gun hydrodynamic, electroporation or nucleofection microinjection
- biolistics biolistics.
- Various gene delivery methods are discussed in detail by Nayerossadat et al. (Adv Biomed Res. 2012; 1: 27) and Ibraheem et al. (Int J Pharm. 2014 Jan l;459(l-2):70-83), incorporated herein by reference.
- nucleic acid modification utilizing the disclosed protein, nucleic acids encoding thereof, systems, or kits.
- the methods may comprise contacting a target nucleic acid sequence with a system, a protein, a nucleic acid, and/or a composition disclosed herein.
- a system a protein, a nucleic acid, and/or a composition disclosed herein.
- the proteins, the gRNA (e.g., coRNA), and the nucleic acids are applicable to the methods described herein.
- nucleic acid modifications refers to modifying at least one physical feature of a nucleic acid sequence of interest.
- Nucleic acid modifications include, for example, single or double strand breaks, deletion, or insertion of one or more nucleotides, and other modifications that affect the structural integrity or nucleotide sequence of the nucleic acid sequence.
- the modifications may include cleavage of the target nucleic acid, excision of the target nucleic acid, integration of the donor nucleic acid, or a combination thereof, as described and outlined in the examples and figures provided herein.
- the methods may comprise excision of a target nucleic acid sequence.
- a system comprising TnpA may be used to site-specifically excise a target DNA sequence.
- the TnpA is derived from a IS607-family transposon.
- the TnpA is a serine family recombinase.
- the target nucleic acid may further be flanked by end sequences, as described above for the donor nucleic acid.
- the methods may comprise insertion of a donor nucleic acid.
- systems comprising TnpA, or a combination of TnpA and TnpB, for example may be sued for RNA-guided DNA integration.
- the methods may comprise cleavage of the target nucleic acid sequence.
- a system comprising TnpB for example, may result in RNA-guided DNA cleavage of the target nucleic acid.
- IStrons may also serve as platforms for introducing selection markers, facilitating their placement within any gene, even those categorized as essential.
- IStrons can splice at the RNA level, resembling the characteristics of group I introns.
- the IStrons encode TnpB or IscB and optionally TnpA or a guide RNA (e.g., coRNA), and may further include an exogenous cargo nucleic acid (e.g., selection marker, gene of interest, etc.
- These elements may be used to integrate exogenous nucleic acids in a wide variety of genomic locations in a range of species (e.g., using conventional genome editing techniques) or the methods disclosed herein. Once integrated, the IS element adopts the role of an adaptive 'gene drive'.
- group I introns comprising an exogenous nucleic acid sequence.
- the group I intron is self-splicing.
- the group I intron is derived from an IS607 element.
- the group I intron is derived from Clostridium botulinum.
- the group I intron further comprises one or more of TnpA, TnpB, IscB, or a guide RNA (e.g., coRNA).
- Modifying a nucleic acid sequence may further comprise any or all of the functions provided by the effector polypeptide as described above.
- any of the TnpA, TnpB, or IscB may be provided with a linked or conjugated effector polypeptide which will modify the target nucleic acid sequence accordingly.
- the TnpA, TnpB, or IscB are provided as a fusion protein.
- TnpA, TnpB, or IscB include a binding moiety which associates with a moiety on the effector polypeptide to form a conjugate in situ.
- the target nucleic acid sequence may be in a cell.
- the contacting a target nucleic acid sequence comprises introducing the system, composition, or proteins into the cell.
- the cell is a mammalian cell.
- the cell is a human cell.
- the target nucleic acid is a nucleic acid endogenous to a target cell.
- the target nucleic acid is a genomic DNA sequence.
- genomic refers to a nucleic acid sequence (e.g., a gene or locus) that is located on a chromosome in a cell.
- the target nucleic acid encodes a gene or gene product
- gene product refers to any biochemical product resulting from expression of a gene.
- Gene products may be RNA or protein.
- RNA gene products include non-coding RNA, such as tRNA, rRNA, micro RNA (miRNA), and small interfering RNA (siRNA), and coding RNA, such as messenger RNA (mRNA).
- mRNA messenger RNA
- the target nucleic acid sequence encodes a protein or polypeptide.
- Polynucleotides containing the target nucleic acid sequence may include, but is not limited to, purified chromosomal DNA, total cDNA, cDNA fractionated according to tissue or expression state (e.g., after heat shock or after cytokine treatment other treatment) or expression time (after any such treatment) or developmental stage, plasmid, cosmid, BAG, YAC, phage library, etc.
- Polynucleotides containing the target site may include DNA from organisms such as Homo sapiens, Mus domesticus, Mus spretus, Canis domesticus, Bos, Caenorhabditis elegans, Plasmodium falciparum, Plasmodium vivax, Onchocerca volvulus, Bntgia malayi, Dirofilaria immitis, Leishmania, Zea maize, Arabidopsis thaliana, Glycine max, Drosophila melanogaster, Saccharomyces cerevisiae, Schizosaccharomyces pombe, Neurospora, Escherichia coli, Salmonella typhimurium, Bacillus subtilis, Neisseria gonorrhoeae, Staphylococcus aureus, Streptococcus pneumonia, Mycobacterium tuberculosis, Aquifex, Thermus aquations, Pyrococcus juriosus, Thermus littoralis, Methano
- the methods may comprise administering to the subject, in vivo, or by transplantation of ex vivo treated cells, an effective amount of the described system.
- the vectors is delivered to the tissue of interest by, for example, an intramuscular, intravenous, transdermal, intranasal, oral, mucosal, or other delivery methods.
- the proteins, composition, components of the present system or ex vivo treated cells may be administered with a pharmaceutically acceptable carrier or excipient as a pharmaceutical composition.
- the components of the present system may be mixed, individually or in any combination, with a pharmaceutically acceptable carrier to form pharmaceutical compositions, which are also within the scope of the present disclosure.
- an effective amount of the components of the present system or compositions as described herein can be administered.
- the term “effective amount” may be used interchangeably with the term “therapeutically effective amount” and refers to that quantity that is sufficient to result in a desired activity upon administration to a subject in need thereof.
- the term “effective amount’ ’ refers to that quantity of the components of the system such that successful DNA modification is achieved.
- the effective amount may depend on the particular condition being treated, the severity of the condition, the individual patient parameters including age, physical condition, size, gender and weight, the duration of the treatment, the nature of concurrent therapy (if any), the specific route of administration and like factors within the knowledge and expertise of the health practitioner.
- the effective amount alleviates, relieves, ameliorates, improves, reduces the symptoms, or delays the progression of any disease or disorder in the subject.
- the subject is a human.
- the terms “treat,” “treatment,” and the like mean to relieve or alleviate at least one symptom associated with such condition, or to slow or reverse the progression of such condition.
- the term “treat” also denotes to arrest, delay the onset (e.g., the period prior to clinical manifestation of a disease) and/or reduce the risk of developing or worsening a disease.
- the term “treat” may mean eliminate or reduce a patient's tumor burden, or prevent, delay, or inhibit metastasis, etc.
- compositions and/or cells of the present disclosure refers to molecular entities and other ingredients of such compositions that are physiologically tolerable and do not typically produce untoward reactions when administered to a subject (e.g., a mammal, a human).
- a subject e.g., a mammal, a human
- pharmaceutically acceptable means approved by a regulatory agency of the Federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in mammals, and more particularly in humans.
- “Acceptable” means that the carrier is compatible with the active ingredient of the composition (e.g., the nucleic acids, vectors, cells, or therapeutic antibodies) and does not negatively affect the subject to which the compositions) are administered.
- Any of the pharmaceutical compositions and/or cells to be used in the present methods can comprise pharmaceutically acceptable carriers, excipients, or stabilizers in the form of lyophilized formations or aqueous solutions.
- Pharmaceutically acceptable carriers including buffers, are well known in the art, and may comprise phosphate, citrate, and other organic acids; antioxidants including ascorbic acid and methionine; preservatives; low molecular weight polypeptides; proteins, such as serum albumin, gelatin, or immunoglobulins; amino acids; hydrophobic polymers; monosaccharides; disaccharides; and other carbohydrates; metal complexes; and/or non-ionic surfactants. See, e.g., Remington: The Science and Practice of Pharmacy 20th Ed. (2000) Lippincott Williams and Wilkins, Ed. K. E. Hoover.
- the methods may be used for a variety of purposes.
- the methods may include, but are not limited to, inactivation of a microbial gene, RNA-guided DNA integration in a plant or animal cell, methods of treating a subject suffering from a disease or disorder.
- the disclosed methods may modify a target DNA sequence in a cell so as to modulate expression of the target DNA sequence, e.g., expression of the target DNA sequence is increased, decreased, or completely eliminated (e.g., via deletion of a gene).
- the modifications of the target sequence may lead to, for example, gene correction, gene replacement, gene tagging, transgene insertion, nucleotide deletion/addition/correction, gene disruption, gene mutation, gene knock-down, etc.
- the methods described herein may be used to genetically modify a plant or plant cell.
- genetically modified plants include a plant into which has been introduced an exogenous polynucleotide.
- Genetically modified plants also include a plant that has been genetically manipulated such that endogenous nucleotides have been altered to include a mutation, such as a deletion, an insertion, a transition, a transversion, or a combination thereof. For instance, an endogenous coding region could be deleted. Such mutations may result in a polypeptide having a different amino acid sequence than was encoded by the endogenous polynucleotide.
- Another example of a genetically modified plant is one having an altered regulatory sequence, such as a promoter, to result in increased or decreased expression of an operably linked endogenous coding region.
- the genetically modified plant may promote a desired phenotypic or genotypic plant trait.
- Genetically modified plants can potentially have improved crop yields, enhanced nutritional value, and increased shelf life. They can also be resistant to unfavorable environmental conditions, insects, and pesticides.
- the present systems and methods have broad applications in gene discovery and validation, mutational and cisgenic breeding, and hybrid breeding. The present methods may facilitate the production of a new generation of genetically modified crops with various improved agronomic traits such as herbicide resistance, herbicide tolerance, drought tolerance, male sterility, insect resistance, abiotic stress tolerance, modified fatty acid metabolism, modified carbohydrate metabolism, modified seed yield, modified oil percent, modified protein percent, resistance to bacterial disease, disease (e.g. bacterial, fungal, and viral) resistance, high yield, and superior quality.
- bacterial disease e.g. bacterial, fungal, and viral
- the present methods may also facilitate the production of a new generation of genetically modified crops with optimized fragrance, nutritional value, shelf-life, pigmentations (e.g., lycopene content), starch content (e.g., low- gluten wheat), toxin levels, propagation and/or breeding and growth time.
- pigmentations e.g., lycopene content
- starch content e.g., low- gluten wheat
- toxin levels propagation and/or breeding and growth time.
- the present method may confer one or more of the following traits to the plant cell: herbicide tolerance, drought tolerance, male sterility, insect resistance, abiotic stress tolerance, modified fatty acid metabolism, modified carbohydrate metabolism, modified seed yield, modified oil percent, modified protein percent, resistance to bacterial disease, resistance to fungal disease, and resistance to viral disease.
- the present disclosure provides for a modified plant cell produced by the present method, a plant comprising the plant cell, and a seed, fruit, plant part, or propagation material of the plant.
- Transformed or genetically modified plant cells of the present disclosure may be as populations of cells, or as a tissue, seed, whole plant, stem, fruit, leaf, root, flower, stem, tuber, grain, animal feed, a field of plants, and the like.
- the present disclosure provides a transgenic plant.
- the transgenic plant may be homozygous or heterozygous for the genetic modification.
- transformed or genetically modified plant cells, tissues, plants, and products that contain the transformed or genetically modified plant cells are also encompasses the progeny, clones, cell lines or cells of the transgenic plants.
- the transformed or genetically modified cells, and tissues and products comprise a nucleic acid integrated into the genome, and production by plant cells of a gene product due to the transformation or genetic modification.
- DNA constructs can be introduced into plant cells by various methods, including, but not limited to PEG- or electroporation-mediated protoplast transformation, tissue culture or plant tissue transformation by biolistic bombardment, or the Agrobacterium-mediated transient and stable transformation.
- the transformation can be transient or stable transformation. Suitable methods also include viral infection (such as double stranded DNA viruses), transfection, conjugation, protoplast fusion, electroporation, particle gun technology, calcium phosphate precipitation, direct microinjection, silicon carbide whiskers technology, Agrobacterium-mediated transformation, and the like.
- Transformation methods based upon the soil bacterium Agrobacterium tumefaciens are useful for introducing an exogenous nucleic acid molecule into a vascular plant
- the wild-type form of Agrobacterium contains a Ti (tumor-inducing) plasmid that directs production of tumorigenic crown gall growth on host plants.
- An Agrobacterium-based vector is a modified form of a Ti plasmid, in which the tumor inducing functions are replaced by the nucleic acid sequence of interest to be introduced into the plant host.
- Agrobacterium-mediated transformation generally employs cointegrate vectors or binary vector systems, in which the components of the Ti plasmid are divided between a helper vector, which resides permanently in the Agrobacterium host and carries the virulence genes, and a shuttle vector, which contains the gene of interest bounded by T-DNA sequences.
- binary vectors are well known in the art and are commercially available, for example, from Clontech (Palo Alto, Calif.).
- Methods of coculturing Agrobacterium with cultured plant cells or wounded tissue such as leaf tissue, root explants, hypocotyledons, stem pieces or tubers, for example, also are well known in the art. See., e.g., Glick and Thompson, (eds.), Methods in Plant Molecular Biology and Biotechnology, Boca Raton, Fla.: CRC Press (1993), incorporated herein by reference.
- the present methods may be adapted to use in plants.
- the vectors may be optimized for transient expression of the present system in plant protoplasts, or for stable integration and expression in intact plants via the Agrobacterium-mediated transformation.
- the present methods use a monocot promoter to drive the expression of one or more components of the present systems (e.g., gRNA) in a monocot plant.
- the present methods use a dicot promoter to drive the expression of one or more components of the present systems (e.g., gRNA) in a dicot plant.
- the present methods may be used with various microbial species, including human pathogens that are medically important, and bacterial pests that are key targets within the agricultural industry , as well as antibiotic resistant versions thereof.
- the method may be designed to target any gene or any set of genes, such as virulence or metabolic genes, for clinical and industrial applications in other embodiments.
- the present systems and methods may be used to inactivate microbial genes.
- the gene is an antibiotic resistance gene.
- the methods described here also provide for treating a disease or condition in a subject.
- a disease-associated gene may be expressed at an abnormally high level or at an abnormally low level, where the altered expression correlates with the occurrence and/or progression of the disease.
- a disease-associated gene also refers to a gene, the mutation or genetic variation of which is directly responsible or is in linkage disequilibrium with a gene(s) that is responsible for the etiology of a disease.
- genes responsible for such “single gene” or “monogenic” diseases include, but are not limited to, adenosine deaminase, a-1 antitrypsin, cystic fibrosis transmembrane conductance regulator (CFTR), ⁇ -hemoglobin (HBB), oculocutaneous albinism II (OCA2), Huntingtin (HIT), dystrophia myotonica-protein kinase (DMPK), low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), neurofibromin 1 (NF1), polycystic kidney disease 1 (PKD1), polycystic kidney disease 2 (PKD2), coagulation factor VIII (F8), dystrophin (DMD), phosphate-regulating endopeptidase homologue, X-linked (PHEX), methyl-CpG-binding protein 2 (MECP2), and ubiquitin-specific peptidase 9Y, Y-linked (USP9Y
- the target genomic DNA sequence can comprise a gene, the mutation of which contributes to a particular disease in combination with mutations in other genes. Diseases caused by the contribution of multiple genes which lack simple (i.e., Mendelian) inheritance patterns are referred to in the art as a “multifactorial” or “polygenic” disease.
- multifactorial or polygenic diseases include, but are not limited to, asthma, diabetes, epilepsy, hypertension, bipolar disorder, and schizophrenia. Certain developmental abnormalities also can be inherited in a multifactorial or polygenic pattern and include, for example, cleft lip/palate, congenital heart defects, and neural tube defects.
- the target DNA sequence can comprise a cancer oncogene.
- the present disclosure provides for gene editing methods that can ablate a disease-associated gene (e.g., a cancer oncogene), which in turn can be used for in vivo gene therapy for patients.
- the gene editing methods include donor nucleic acids comprising therapeutic genes.
- kits that include the components of the present system, such as a TnpA protein, a TnpB protein, an IscB protein, and/or a guide RNA (e.g., CDRNA).
- a guide RNA e.g., CDRNA
- the kit may include instructions for use in any of the methods described herein.
- the instructions can comprise a description of administration of the present system or composition to a subject to achieve the intended effect.
- the instructions generally include information as to dosage, dosing schedule, and route of administration for the intended treatment.
- the kit may further comprise a description of selecting a subject suitable for treatment based on identifying whether the subject is in need of the treatment
- kits provided herein are in suitable packaging.
- suitable packaging includes, but is not limited to, vials, bottles, jars, flexible packaging, and the like.
- Kits optionally may provide additional components such as buffers and interpretive information.
- the kit comprises a container and a label or package insert(s) on or associated with the container.
- the disclosure provides articles of manufacture comprising contents of the kits described above.
- the kit may further comprise a device for holding or administering the present system.
- the device may include an infusion device, an intravenous solution bag, a hypodermic needle, a vial, and/or a syringe.
- IscB and TnpB detection and database curation Homologs of IscB proteins were comprehensively detected using the amino acid sequence of a K. racemifer homolog (NCBI Accession: WP_007919374.1) as the seed query in a JackHMMER part of the HMMER suite (v3.3.2).
- NCBI Accession: WP_007919374.1 the seed query in a JackHMMER part of the HMMER suite (v3.3.2).
- a conservative inclusion and reporting threshold of le-30 was used in the iterative search against the NCBI NR database (retrieved on 06/11/2021), resulting in 5,715 hits after convergence.
- These putative homologs were then annotated to profiles of known protein domains from the Pfam database (retrieved on 06/29/2021) using hmmscan with an E-value threshold of le-5.
- Proteins that did not contain the RRXRR, RuvC, RuvCjn, or the RuvX domain were discarded. Although the HNH domain was annotated, proteins without the HNH were not removed. The variation in the presence of the HNH domain was preserved to better represent the natural diversity of IscBs. From the remaining set, proteins that were less 250 aa were removed to eliminate partial or fragmented sequences, resulting in a database of 4,674 non-redundant IscB homologs. Contigs of all putative iscB loci were retrieved from NCBI for downstream analysis using the Bio.Entrez package.
- TnpB homologs were comprehensively detected similarly to IscB, use both the H. pylori (/TpyTnpB) amino acid sequence (NCBI Accession: WP_078217163.1) and the G. stearothermophilus (Gs'fTnpB2) amino acid sequence (NCBI Accession: WP_047817673.1) as seed queries for two independent iterative jackhammer searches against the NR database, with an inclusion and reporting threshold of le-30. The union of the two searches were taken, and proteins that were less than 250 aa were removed to trim partial or fragmented sequences, resulting in a database of 95,731 non-redundant TnpB homologs. Contigs of all putative tnpB loci were retrieved from NCBI for downstream analysis using the Bio.Entrez package.
- IscB protein sequences were clustered with at least 95% length coverage and 95% alignment coverage using CD-HIT (v4.8.1). The clustered representatives were taken and aligned using MAFFT (v7.508) with the E-INS-I method for 4 rounds. Post-alignment cleaning consisted of using trimAl (vl.4.revl5) to remove columns containing more than 90% of gaps and manual inspection.
- the phylogenetic tree was created using IQ-Tree 2 (v2.1.4) with the WAG model of substitution. Branch support was evaluated with 1000 replicates of SH-aLRT, aBayes, and ultrafast bootstrap support from the 1QTREE package. The tree with the highest maximum-likelihood was used as the reconstruction of the IscB phylogeny.
- TnpB sequences were clustered by 50% length coverage and 50% alignment coverage using CD-HIT. Similar to IscB, the clustered representatives were taken and aligned using MAFFT 55 with the E-INS-I method for 4 rounds. Post-alignment cleaning consisted of using trimAl to remove columns containing more than 90% of gaps and manual inspection.
- the phylogenetic tree was created using IQ-Tree 2 with the WAG model of substitution. Branch support was evaluated with 1000 replicates of SH-aLRT, aBayes, and ultrafast bootstrap support from the IQTREE package. The tree with the highest maximum-likelihood was used as the reconstruction of the TnpB phylogeny.
- This covariance model was used to expand the 3’ coordinates of previously identified coRNAs to encompass the second stem loop using cmsearch on expanded toRNAs. These refined toRNA boundaries and sequences were then used to create a new ooRNA model. The refined mRNAs were clustered by 99% length coverage and 99% alignment coverage using CD-HIT to remove duplicates. A structure-based multiple alignment was then performed using mLocARNA (vl.9.1) with the following parameters:
- the resulting alignment with structural information was used to generate a new coRNA covariance model with the Infernal suite, refined with Expectation-Maximization from CMfinder, and verified with R-scape at an E-value threshold of le-5.
- the resulting coRNA covariance model was used with cmsearch to discover new coRNAs within the curated IscB- associated contig database.
- the resulting sequences were aligned to generate a new CM model that was used to again search the IscB-associated contig database. This process was repeated three times for the final generic IscB-associated toRNA model.
- Each protein was used as a seed query in a phmmer (v3.3.2) search against the NR database, with an inclusion and reporting threshold of le-30 to identify close relatives of each protein.
- the steps described above were used to define transposon boundaries and generate mRNA models using sequences identified in the phmmer search.
- TnpA detection and autonomous element identification For both IscB- and TnpB- associated contigs, TnpA was detected using the Pfam YI Tnp (PF01797) for a hmmsearch from the HMMR suite (v3.3.2), with an E-value threshold of le-4. This search was performed independently on both the curated CDSs of each contig from NCBI and the ORFs predicted by Prodigal on default settings. The union of these searches was used as the final set of detected TnpA proteins. IS elements that encoded IscB homologs within 1,000 bp of a detected TnpA, or that encoded TnpB homologs within 10,000 bp of a detected TnpA, were defined as autonomous. Analysis which uncovered association with serine resolvases (PF00239) was performed with the same parameters mentioned above.
- Orientation bias analysis The closest NCBI-annotated/predicted CDS upstream of each transposon-encoded gene (tnpBHscB or the IS630 transposase) was retrieved and analyzed relative to the gene itself. Initially, the metadata for every NCBI-annotated CDS within contigs containing these genes (tnpBHscB or IS630) were retrieved, including coordinates and strandedness. Using this information, the closest upstream CDS was identified for each gene based on distance. Then, the annotated orientation of the closest upstream CDS was compared to the annotated orientation of the respective transposon-encoded gene (tnpBHscB or IS630), to determine whether they were matching.
- transposon ends were initially paired with the most similar query end and then manually curated, to ensure each the LE and RE within a given pair were correctly positioned relative to each other.
- This analysis identified several P ATE-like elements lacking any protein-coding genes, and a total of 47 IS elements were identified with similar LE and RE sequences.
- 50 bp upstream and downstream were extracted and aligned using MUSCLE (5.1) PPP algorithm in Geneious and trimmed using trimAl (vl.4.revl5), to capture transposon boundaries and identify TAM and TEM motifs based on previous literature describing the location of these essential motifs.
- Transposon DNA guide regions were predicted based on structural similarities to the transposon ends of H. pylori AS608 and covarying mutations at those predicted locations.
- TAM motifs which function as target sites for the transposon insertion event, were confirmed by blastn analysis of DNA sequences flanking predicted transposon boundaries to the NT or WGS database. Phylogenetic trees of transposon ends were built using FastTree (2.1.11) with default parameters.
- RNA-seq analyses Small RNA-seq analyses. Small RNA-seq reads were retrieved from NCBI SRA database under accession SRX3260293. Reads were downloaded using the SRA toolkit (2.11.0) and mapped to genomic regions encoding G. stearothermophilus IscB and TnpB homologs used in this study, using G. stearothermophilus strain ATCC 7953 (GCA_000705495.1) from which small RNA-seq data derives. Reads were mapped using Geneious RNA assembler at medium sensitivity and visualized using Integrative Genomics Viewer.
- Plasmid construction All plasmids used in this study are described in Tables 7 and 8. In brief, genes encoding TnpA, TnpB, and IscB homologs from G. stearothermophilus, H. pylori and/). radiodurans were synthesized by GenScript, along mini-Tn elements containing a chloramphenicol resistance gene. To generate mini-Tn plasmids, gene fragments (GenScript) encoding the transposase (TnpA) downstream of a lac and T7 promoter, and transposon ends flanking a chloramphenicol resistance gene, were cloned into EcoRI sites of pUC57.
- GeneScript gene fragments encoding the transposase (TnpA) downstream of a lac and T7 promoter, and transposon ends flanking a chloramphenicol resistance gene
- Gene gene fragments (Genscript) of mRNA encoded downstream of T7 promoter, along with tnpB or iscB also encoded downstream of T7 promoter, were cloned into pCDF- Duetl vectors at Pfol and Bsu36I sites. Oligonucleotides containing J23-series promoters were cloned into Sall and Kpnl sites, replacing the T7 promoter for coRNA expression, or into Pfol- Xhol sites, replacing the T7 promoter for tnpB expression.
- pTarget plasmids were generated using a minimal pCOLADuet-1, generated by around-the-hom PCR to create a minimal pCOLA- Duet-1 containing only the ColA origin of replication and kanamycin resistance gene.
- This vector was then used to generate pTargets encoding 45-bp target sites by around-the-hom PCR Derivatives of these plasmids were cloned using a combination of methods, including Gibson assembly, restriction digestion-ligation, ligation of hybridized oligonucleotides, and around-the- hom PCR Plasmids were cloned, propagated in NEB Turbo cells (NEB), purified using Miniprep Kits (Qiagen), and verified by Sanger sequencing (GENEWIZ).
- the cell debris was pelleted by centrifugation at 4,000g for 5 min, and 10 pl of lysate supernatant was removed and serially diluted with 90 pl of HzO to generate 10- and 100- fold lysate dilutions for PCR and qPCR analysis.
- IS element excision from the plasmid backbone was detected by PCR using OneTaq 2X Master Mix with Standard Buffer (NEB) and 0.2 uM primers, designed to anneal upstream and downstream of the IS element PCR reactions contained 0.5 pl of each primer at 10 pM, 12.5 pl of OneTaq 2X MasterMix with Standard Buffer, 2 pl of 100-fold diluted cell lysate serving as template, and 9.5 pl of HzO. The total volume per PCR was 25 pl.
- lysate was prepared as described above but harvested from LB-agar containing carbenicillin (100 ⁇ g ml -1 ), spectinomycin (100 ⁇ g ml -1 ) , and X-gal (200 mg ml"" 1 ) in transposition assays combining TnpA and TnpB, as described below. Measurements were performed in a BioRad T100 thermal cycler using the following thermal cycling parameters: DNA denaturation (94 °C for 30 s), 26 cycles of amplification (annealing: 52 °C for 20 s, extension: 68 °C for 1:15 min), followed by a final extension (68 °C for 5 min).
- Reactions were prepared in 384- well clear/white PCR plates (BioRad), and measurements were performed on a CFX384 RealTime PCR Detection System (BioRad) using the following thermal cycling parameters to selectively amplify excision products: polymerase activation and DNA denaturation (98 °C for 2.5 min), 40 cycles of amplification (98 °C for 10 s, 62 °C for 20 s), and terminal melt-curve analysis (65-95 °C in 0.5 °C per 5 s increments).
- lysates were prepared from cells harboring a plasmid containing a mock excised mini-Tn substrate (pSL4826) and a plasmid containing the mini-Tn but lacking an active TnpA transposase required for excision (pSL4735).
- Variable IS element excision frequencies were simulated across five orders of magnitude (ranging from 0.002% to 100%) by mixing cell lysates the control strain and the IS-encoding strain in various ratios, which demonstrated accurate detection of excision products in genomic IS element excision assays in vivo to a frequency of 0.001 (FIG 8D).
- IS element excision frequencies of genomically integrated mini-TN were quantified by qPCR using SsoAdvancedTM Universal SYBR Green Supermix (BioRad) (FIG. 12).
- Cells were harvested from LB containing carbenicillin (100 ⁇ g ml -1 ), spectinomycin (100 ⁇ g ml -1 ), and X-gal (200 mg ml -1 ), as described above.
- qPCR analysis was performed using transposon flanking- and genome-specific primers.
- Transposon flanking primers were designed to amplify an approximately 209-bp fragment upon excision.
- lysates were prepared from a control MG1655 strain, and a strain containing a genomically-encoded IS element that disrupts the lacZ gene. Similar to the plasmid-based assay, variable IS element excision frequencies were simulated across five orders of magnitude (ranging from 0.002% to 100%) by mixing cell lysates the control strain and the IS-encoding strain in various ratios, and showed accurate detection of excision products in genomic IS element excision assays in vivo to a frequency of 0.001 (FIG. 12B).
- sSLl 592 harbors a mini-F plasmid derivative with an integrated spectinomycin cassette. This strain was transformed with a plasmid carrying a mini-Tn harboring a kanamycin marker and either GstTnpA (pSL4245) or catalytically inactive GsfTnpA (pSL4974). Cells were selected on LB media containing spectinomycin (100 ⁇ g ml -1 ), carbenicillin (100 ⁇ g ml -1 ), and kanamycin (50 ⁇ g ml -1 ) to generate a donor strain.
- Cells were 100-fold diluted into fresh liquid LB media with respective antibiotics and grown for 2 h to ⁇ 0.5 OD. Cells were then washed with H2O and mixed at a concentration of 5 X 10 7 for both donor and recipient cells, and plated onto solid LB-agar media with no antibiotic selection. Cells were grown for 20 h at 37 °C, scraped off plates, and resuspended in H2O.
- Cells were then serially diluted and plated onto LB media containing rifampicin (100 pg/mL), nalidixic acid (30 pg/mL), spectinomycin (100 ⁇ g ml -1 ), and kanamycin (50 ⁇ g ml -1 ) to monitor transposition.
- rifampicin 100 ⁇ g ml -1
- nalidixic acid 30 ⁇ g ml -1
- spectinomycin 100 ⁇ g ml -1
- the frequency of transposition was calculated by taking the number of colonies that exhibited Nal R + Rif* + Spec R + Kan R phenotype (e.g., transposition positive), divided by the number of transconjugants that exhibited a Nal R + Rif* + Spec® phenotype.
- Transconjugants showing resistance to nalidixic acid, rifampicin, spectinomycin, and kanamycin were isolated using Zymo Research ZR BAC DNA miniprep kit and sequenced using nanopore long-read sequencing (Plasmidsaurus). Reads were analyzed in Geneious Prime (2023.0.1) by using a custom blast database to identify reads containing mini-Tn and flanking mini-F plasmid sequence. Insertion events were aligned to Mini-F plasmid reference to identify sites of integration.
- Plasmid interference assays Plasmid interference assays were performed in E. colt BL21 (DE3) (FIGS. 3C, 3F, 10A-10B, and 10D) orEcoli str. K-12 substr. MG1655 (sSL0810) strains for all other experiments.
- FIG. 3C TnpB homologs
- BL21 (DE3) cells were transformed with pTarget plasmids, and single colony isolates were selected to prepare chemically competent cells. 400 ng of pEffector plasmids were then delivered via transformation. After 3 h, cells were spun down at 4000 g for 5 min and resuspended in 20 pl of H2O.
- Cells were then serial diluted (lOx) and transferred to LB media containing spectinomycin (100 ⁇ g ml -1 ), kanamycin (50 ⁇ g ml -1 ), and 0.05 mM IPTG and grown for 14 h at 37 °C. Plates were imaged in an Amersham Imager 600.
- Quantification of plasmid interference was calculated by determining the number of colony forming units (CPUs) following transformation.
- Cells were first transformed with pEffector plasmids and prepped as chemically competent cells for a second round of transformation with 200 ng of pTarget. Cells were then spun down at 4000 g for 5 min and resuspended in 100 pL of H2O. Cells were then serial diluted and plated to LB media containing spectinomycin (100 ⁇ g ml -1 ), kanamycin (50 ⁇ g ml -1 ). 0.05 mM IPTG was added to media when T7 promoter was used. CPUs were counted following 24 h of growth at 37 °C.
- Genome targeting and cell killing assays were performed by transforming E. coli str. K- 12 substr. MG1655 (sSL0810) strains with spectinomycin-resistant plasmids constitutively expressing TnpB/IscB and either genomic targeting or non-targeting guide RNAs. Cells were transformed with 400 ng plasmid. After 3 h, cells were spun down at 4000 g for 5 min and resuspended in 20 ⁇ l of EbO. Cells were then serial diluted (lOx) and transferred to LB media containing spectinomycin (100 ⁇ g ml -1 ) and grown for 24 h at 37 °C.
- ChlP-seq experiments and library preparation were generally performed as described previously (See, Hoffmann, F. T. et al, Nature 609, 384-393 (2022), incorporated herein by reference).
- the following active site mutations were introduced to inactivate the endonuclease domains of the respective 3xFlag-tagged proteins to simulate DNA binding prior to DNA cleavage: GstlscB (D87A, H238A, H239A); GstTnpB (D196A); SpyCas9 (D10A, H840A); AsCasl2a (D908A).
- coli BL21(DE3) cells were transformed with a single plasmid encoding the catalytically inactive effector and either a lacZ targeting raRNA or nontargeting oiRNA. After incubation for 16 h at 37°C on LB agar plates with antibiotics (200 pg ml -1 spectinomycin), cells were scraped and resuspended in 1 ml of LB.
- the optical density at 600 nm (OD600) was measured, and approximately 4.0 x 10 8 cells (equivalent to 1 ml with an OD600 of 0.25) were spread onto two LB agar plates containing antibiotics (200 pg ml" 1 spectinomycin) and supplemented with 0.05 mM IPTG Plates were incubated at 37°C for 24 h. All cell material from both plates was scraped and transferred to a 50 ml conical tube.
- Cross-linking was performed by mixing 1 ml of formaldehyde (37% solution; Thermo Fisher Scientific) to 40 ml of LB medium (-1% final concentration) followed by immediate resuspension of the scraped cells by vortexing and 20 min of gentle shaking at room temperature. Cross-linking was stopped by the addition of 4.6 ml of 2.5 M glycine (-0.25 M final concentration) followed by 10 min incubation with gentle shaking. Cells were pelleted at 4°C by centrifuging at 4,000g for 8 min. The following steps were performed on ice using buffers that had been sterile-filtered.
- the samples were sonicated on a M220 Focused-ultrasonicator (Covaris) with the following SonoLab 7.2 settings: minimum temperature, 4 °C; set point, 6 °C; maximum temperature, 8 °C; peak power, 75.0; duty factor, 10; cycles/bursts, 200; 17.5 min sonication time.
- samples were cleared of cell debris by centrifugation at 20,000 g and 4 °C for 20 min. The pellet was discarded, and the supernatant ( ⁇ 1 ml) was transferred into a fresh tube and kept on ice for immunoprecipitation.
- 10 pl ⁇ 1%
- 10 pl 10 pl ( ⁇ 1%) of the sheared cleared lysate were transferred into a separate 1.5 ml tube, flash-frozen in liquid nitrogen and stored at -80 °C.
- the conjugation mixture of magnetic beads and antibodies was washed four times with BSA solution as described above, but at 4 °C.
- the beads were resuspended in 30 pl (x n samples) FA lysis buffer 150 with protease inhibitor, and 31 pl of resuspended antibody-conjugated beads were mixed with each sample of sheared cell lysate.
- the samples rotated overnight for 12-16 h at 4 °C for immunoprecipitation of Flag-tagged proteins.
- tubes containing beads were placed on a magnetic rack, and the supernatant was discarded.
- the beads were then placed onto a magnetic rack, the supernatant was removed, and the beads were resuspended in 200 ⁇ l of fresh ChIP elution buffer (1% (w/v) SDS, 0.1 MNaHCO3).
- ChIP elution buffer 1% (w/v) SDS, 0.1 MNaHCO3
- the suspensions were incubated at 65 °C for 1.25 h with gentle vortexing every 15 min to resuspend settled beads. During this incubation, the nonimmunoprecipitated input samples were thawed, and 190 ⁇ l of ChIP Elution Buffer was added, followed by the addition of 10 ⁇ l of 5 M NaCl.
- the tubes were placed back onto a magnetic rack, and the supernatant containing eluted protein-DNA complexes was transferred to a new tube. Then, 9.75 pl of 5 M NaCl was added to -195 pl of eluate, and the samples (both immunoprecipitated and non-immunoprecipitated controls) were incubated at 65 °C overnight to reverse-cross-link proteins and DNA.
- samples were mixed with 1 pl of 10 mg ml" 1 RNase A (Thermo Fisher Scientific) and incubated for 1 h at 37 °C, followed by addition of 2.8 pl of 20 mg ml -1 proteinase K (Thermo Fisher Scientific) and 1 h incubation at 55 °C.
- buffer PB QIAGEN recipe
- the samples were purified using QIAquick spin columns (QIAGEN) and eluted in 40 ⁇ l TE buffer 10/0.1 (10 mM Tris-HCl pH 8.0, 0.1 mM EDTA).
- ChlP-seq Illumina libraries were generated for immunoprecipitated and input samples using the NEBNext Ultra II DNA Library Prep Kit for Illumina (NEB). Sample concentrations were determined using the DeNovix dsDNA Ultra High Sensitivity Kit. Starting DNA amounts were standardized such that an approximately equal mass of all input and immunoprecipitated DNA was used for library preparation.
- PCR amplification (12 cycles) was performed to add Illumina barcodes, and -450 bp DNA fragments were selected using two-sided AMPure XP bead (Beckman Coulter) size selection, as follows: the volume of barcoded immunoprecipitated and input DNA was brought up to 50 pl with TE Buffer 10/0.1 ; in the first size-selection step, 0.55x AMPure beads (27.5 pl) were added to the DNA, the sample was placed onto a magnetic rack, and the supernatant was discarded and the AMPure beads were retained; in the second size-selection step, 0.35x AMPure beads (17.5 pl) were added to the DNA, the sample was placed onto a magnetic rack, and the AMPure beads were discarded and the supernatant was retained. The concentration of DNA was determined for pooling using the DeNovix dsDNA High Sensitivity Kit
- Illumina libraries were sequenced in paired-end mode on the Illumina MiniSeq and NextSeq platforms with automated demultiplexing and adapter trimming (Illumina). For each ChlP-seq sample, >1,000,000 raw reads (including genomic and plasmid-mapping reads) were obtained.
- ChlP-seq data analyses ChlP-seq data analyses. ChlP-seq data analysis was generally performed as described previously (See, Hoffmann, F. T. et al, Nature 609, 384-393 (2022), incorporated herein by reference). In brief, ChlP-seq paired-end reads were trimmed and mapped to an E. coll BL21(DE3) reference genome (GenBank: CP001509.3). Genomic lacZ and lacl regions, partially identical to plasmid-encoded genes, were masked in all alignments (genomic coordinates: 335,600-337,101 and 748,601-750,390).
- the corresponding 200-bp sequence for each peak was extracted from the E. coll reference genome using the command bedtools getfasta. Sequence motifs were determined using MEME ChlP. Individual off-target sequences (FIG. 11) represent sequences from the top enriched peaks determined by MACS3 that contain the MEME ChlP motif.
- TAM library cloning TAM libraries were cloned containing a 6-bp randomized sequence between the native target sequences for GsflscB (ISGstJ) and GstTnpB2 (!SGst2).
- two partially overlapping oligos oSL9404 and oSL9405 were annealed by heating to 95 °C for 2 min and then cooled to room temperature.
- One of these oligos (oSL9404) contained a tint degenerate sequence flanked by target sites for GrtTnpB2 and GsflscB.
- Annealed DNA was treated with DNA Polymerase I, Large (Klenow) Fragment (NEB) in 40
- Double-stranded insert DNA and vector backbone pSL4031 was digested with BamHI and Hindlll (37 °C, 1 h). The digested insert was cleaned-up (Qiagen MinElute PCR Purification Kit), and digested backbone was gel-purified (Qiagen QIAquick Gel Extraction Kit). The backbone and insert were ligated with T4 DNA Ligase (NEB).
- Ligation reactions were transformed in with electrocompetent NEB 10-beta cells according to the manufacturer’s protocol. After recovery (37 °C for 1 h), cells were plated on large bioassay plates containing LB agar and kanamycin (50 ⁇ g ml -1 ). Approximately 5 million CPUs were scraped from each plate, representing lOOOx coverage of each library member, and plasmid DNA was isolated using the Qiagen CompactPrep Midi Kit.
- TAM library assays and NGS library prep DNA solutions containing 500 ng of the TAM plasmid library (pSL4841) and 500 ng of plasmids encoding either GsrTnpB2 (pSL4369) or GstlscB (pSL4514) were co-transformed in electrocompetent E. coli BL21(DE3) cells according to the manufacturer’s protocol (Sigma-Aldrich). Cells were serially diluted on large bioassay plates containing LB agar, spectinomycin (100 ⁇ g ml -1 ), and kanamycin (50 ⁇ g ml -1 ). Approximately 600,000 CPUs were scraped from plates, representing lOOx coverage of each library member, and plasmid DNA was isolated using the Qiagen CompactPrep Midi
- Illumina amplicon library for NGS was prepared through 2-step PCR amplification. In brief, ⁇ 50 ng of plasmid DNA recovered from TAM assay was used in each “PCR-1” amplification reaction with primers flanking the degenerate TAM library sequence and containing universal Illumina adaptors as 5’ overhangs. Amplification was carried out using high-Fidelity Q5 DNA Polymerase (NEB) for 16 thermal cycles. Samples from “PCR-1” amplification were diluted 20- fold and amplified for “PCR-2” in 10 thermal cycles with primers contain indexed p5/p7 sequences. Reactions were verified by analytical gel electrophoresis. Sequencing was performed with a paired-end run using a MiniSeq High Output Kit with 150-cycles (Illumina).
- NEB high-Fidelity Q5 DNA Polymerase
- This strain was transformed with either pCDFDuet-1 (pSLOOOT) or various GstTnpB carrying vectors (pSL4369, pSL4664, pSL4518 and pSL4740, see Table 8 for description) and selected on LB agar containing spectinomycin (100 ⁇ g ml -1 ) and kanamycin (50 ⁇ g ml -1 ).
- Single colony isolates of cells harboring each plasmid were prepared chemically competent and transformed with a TnpA expression vector (pSL4529) or a catalytically inactive mutant TnpA expression vector (pSL4534) and selected on LB agar containing carbenicillin (100 ⁇ g ml -1 ), spectinomycin (100 ⁇ g ml -1 ) and kanamycin (50 ⁇ g ml -1 ).
- Cells were grown at 37 °C for 4 days on MacConkey media to enrich for mini-Tn excision events. Cells were then harvested, serially diluted, and plated onto LB agar containing carbenicillin (100 ⁇ g ml -1 ), spectinomycin (100 ⁇ g ml -1 ) and X-gal (200 mg ml -1 ) or carbenicillin (100 ⁇ g ml -1 ), spectinomycin (100 ⁇ g ml -1 ), kanamycin (50 ⁇ g ml -1 ) and X-gal (200 mg ml -1 ) and grown for 18 h at 37 °C. Total number of colonies were counted, along with the number of blue colonies to determine the frequency of excision and reintegration events. In addition, genomic lysate was harvested from cells as described above for PCR analysis.
- Example 1 G stearothermophUus encodes divase TnpB/iscB homologs
- NCBI NR database was mined for TnpBZLscB homologs and phylogenetic trees were built that highlight the diversity of both protein families (FIGS. 6A and 6D).
- flanking genomic regions only a sporadic association with Y1 tyrosine transposases was identified, with -25% of all tnpB genes containing an identifiable tnpA nearby, indicative of autonomous transposons.
- iscB genes were much less abundant than tnpB and rarely associated with tnpA (-1.5%).
- TnpB but not iscB genes were also found associated with an unrelated serine resolvase (also denoted tnpA) that is a hallmark of IS607-family transposons, albeit at a much lower frequency (-8%) (FIG. 6D).
- a conserved intergenic region upstream of iscB was bounded by the transposon right end (RE), and bore similarity to a non-coding RNAs.
- Both IscB and TnpB use these transposon- encoded RNAs, referred to hereafter as coRNAs, as guides to direct cleavage of complementary dsDNA substrates, in a mechanism analogous to Cas9 and Casl 2.
- coRNAs transposon- encoded RNAs
- Covariation models were generated for TnpB- and IscB-specific coRNAs, which revealed the conserved secondary structural motifs characteristic of both guide RNAs (FIGS. IB and 6B), and these models were used to demonstrate the tight genetic linkage between tnpB/iscB genes and flanking coRNA loci (FIGS.
- IscB-specific coRNAs comprise a constant scaffold sequence derived from the transposon RE, joined by a 5 ’-adjacent guide region encoded outside of the transposon boundary, coRNA biogenesis relies on transcription initiating outside of the IS element and proceeding towards the iscB ORF (FIG. 6B).
- Genomic insertions into transcriptionally active target sites may aid in the generation of functional coRNAs, and these insertion products are either preferentially generated (during transposition) or preferentially retained. Notably, this orientation bias was absent for TnpB, whose raRNA substrates rely on transcription that initiates within the IS element itself (described below), and for an unrelated IS630-family transposase that were included as a negative control (FIG. 6C).
- Gst Geobacillus stearothermophilus
- ISGstl-5 a thermophilic soil bacterium
- FIG. 1C Analysis of small RNA sequencing data revealed that coRNAs from multiple transposons were constitutively expressed (FIG. ID), and the left end (LE) and right end (RE) boundaries of these IS elements were highly similar in DNA sequence (FIGS. 7A-7D), suggesting a common mechanism of mobilization.
- a DNA excision assay was designed to test the activity of GstTnpA on a minitransposon (mini-Tn) substrate derived from its native autonomous IS element, ISGstl.
- mini-Tn minitransposon
- E. coli expression vectors that encoded GstTnpA upstream of the mini-Tn, which comprised an antibiotic resistance gene flanked by full-length LE and RE sequences and genomic G. stearothermophilus sequences upstream and downstream of the predicted transposon boundaries were cloned.
- Primers were designed to bind outside the mini-Tn, such that PCR from cellular lysates would amplify either the starting substrate or a shorter reaction product resulting from transposon excision and re-ligation (FIGS. 2A-2B).
- GstTnpA was active on all five families of IS elements, with excision dependent on the predicted catalytic tyrosine residue (FIG. 2C), but failed to cross-react with a DNA substrate derived from an H. pylori IS608 element (FIGS. 8A-8B).
- Sanger sequencing of excision products revealed that in each case, TnpA precisely re-joined sequences flanking the mini-Tn to generate a scarless donor joint (FIG.
- Excision proceeded regardless of whether the mini-Tn was encoded on the leading or lagging-strand template, but was ablated when either the LE or RE sequence were scrambled, confirming the importance of these regions for TnpA recognition. Excision was also strongly dependent on the presence of a cognate TAM adjacent to the LE as well as a compatible DNA ‘guide' sequence located within the LE, since mutation of either region led to a loss of product formation (FIG. 2E). Interestingly, however, simultaneous mutation of both the TAM and LE guide sequence to the corresponding motifs found in IS608 restored excision activity with GstTnpA (FIG. 2F).
- GstTnpB and IscB homologs function as RNA-guided endonucleases
- GstlscB and three GstTnpB distinct homologs were highly active for RNA-guided DNA cleavage of their native donor joints (FIGS. 3C and 3D).
- HpyTnpB encoded by the well-studied IS608 element was inactive when tested under similar conditions, whereas the activity for DraTnpB was confirmed (FIG. 10B).
- TAM on pTarget was systematically mutagenized and DNA cleavage was ablated with even single-bp changes, which would also render the site of coRNA biogenesis at the transposon RE, where the motif differs from the cognate TAM in only two positions, completely unrecognizable (FIGS. 3E-3F and 10C-10D).
- TnpB and IscB were both functional for genomic targeting and cleavage as well, and point mutations in the predicted HNH and/or RuvC nuclease domains completely ablated activity (FIGS. 3G and 3H).
- a panel of three TnpB- specific coRNAs targeting lacZ showed varying levels of activity, as assessed by cell lethality (FIG. 10E).
- Cas9 and Casl 2 may have evolved a greater degree of reliance on RNA-DNA complementarity for stable DNA binding, whereas IscB and TnpB may be dependent on a more extensive TAM motif but permissive of RNA-DNA mismatches.
- RNA-guided nucleases promote transposon retention through targeted DSBs
- Strains were transformed with expression plasmids encoding TnpA (or an inactive mutant) and TnpB (or an inactive mutant), programmed with either a non-targeting mRNA or a lacZ- targeting mRNA designed to cleave the donor joint generated upon TnpA-mediated mini-Tn excision. After enriching for excision events by growing strains on MacConkey agar, cells were plated on media containing X-gal and performed blue- white colony screening.
- TnpB and a ZacZ-specific mRNA completely eliminated the emergence of blue colonies under otherwise identical conditions, and colony PCR confirmed that transposons were uniformly maintained at their original genomic location (FIGS. 5B-5D and 12).
- This phenotypic effect was dependent on both a targeting mRNA and an intact TnpB nuclease domain, indicating that targeting/binding alone is insufficient for transposon retention at the donor site, but that targeted cleavage and local DSB formation facilitate the effect.
- TnpB nucleases preserve transposons at the donor site that are otherwise lost via TnpA-mediated excision, through formation of targeted DSBs and ensuing recombination (FIG. 5E).
- IS Insertion sequences
- TnpA and TnpB are the simplest mobile genetic elements found in bacteria which encode only the genes for their mobilization and retention. Those usually include two open reading frames, namely TnpA and TnpB.
- IS605 and IS607 are two main classes of IS elements, IS605 and IS607, which have homologous tnpB, but evolutionary unrelated tnpA genes.
- IS605 elements harbor a Y1 tyrosine transposase, which mediates transposition via single stranded DNA intermediate.
- IS607 TnpA is a serine resolvase, capable of cleaving and re-joining double stranded DNA.
- TnpA and TnpB homologs are encoded within group I introns, generating chimeric genetic elements called IStrons. These elements are not only mobile on the DNA level, due to TnpA and TnpB, but are phenotypically silent on the RNA level because the whole element is removed during splicing. IStrons can harbor TnpA and TnpB proteins related to either IS605 or IS607, suggesting multiple IS element acquisition events by group I intron during evolution. Some of the IStrons encoding proteins from IS607 elements were found in pathogenic bacteria species of Clostridium botulinum.
- TnpB (CboTnpB) is active for double-stranded DNA cleavage in E. coli.
- TnpB from IS607 elements cleaves DNA when both TAM and target-complementary coRNA guide are present and this activity is dependent on its RuvC active site. The same active site is also responsible for raRNA maturation on the 5’ end.
- the transposase (CboTnpA) associated with this TnpB recognizes CboIStron ends and can excise the element from its native location. Lastly, the CboIStron can self-splice from the E. coli RNA transcript.
- pEffector encodes a codon optimized CboTnpB (or CboTnpB(D190A)) and an coRNA under the control of two separate constitutive promoters on a pCDF-Duet-1 vector.
- target plasmids pTarget
- Representative plasmid sequences are listed in Tables 7 and 8.
- Targeted plasmid DNA cleavage in E. coli Plasmid interference assays were performed in E coli str. K-12 substr. MG1655. The cells were transformed with pEffector plamids and single colony isolates were selected to prepare chemically competent cells. These cells were transformed with 200 ng of pTarget plasmids by heat shocking at 42°C for 30 sec, followed by recovery at 37°C for 1 h. The cells were then spun down at 4000 g for 5 min and resuspended in 30 pl of MilliQ HzO.
- Cells were then serially diluted (lOx) and plated on LB-agar media with spectinomycin (100 ⁇ g ml -1 ) and kanamycin (50 pg ml" 1 ). Cells were grown for 24 h at 37 °C and plates were imaged in an Amersham Imager 600.
- TAM library assays and NGS library prep To unbiasedly determine CboTnpB TAM sequence a plasmid library with 6 degenerate nucleotides 5’ of the target sequence was used. DNA solutions containing 500 ng of the TAM plasmid library (pSL4841) and 500 ng of plasmids encoding either CAoTnpB with a targeting coRNA (pSL5002) or CAoTnpB with a nontargeting coRNA (pSL4902) were co-transformed in electrocompetent E. coli BL21(DE3) cells according to the manufacturer’s protocol (Sigma- Aldrich).
- Amplification was carried out using high-Fidelity Q5 DNA Polymerase (NEB) for 15 thermal cycles. Samples from 1 st step PCR amplification were diluted 20-fold and amplified for 2 nd step PCR in 10 thermal cycles with primers containing indexed p5/p7 sequences. Reactions were verified by analytical gel electrophoresis. Sequencing was performed with a single-end run using a MiniSeq High Output Kit for 75-cycles (Illumina).
- RNA-immunoprecipitation followed by sequencing was used to detect mature coRNA bound by CboTnpB.
- Cells expressing 3xFLAG- CboTnpB and bioinformatically predicted coRNA were grown until they reached an exponential phase, then pelleted, resuspended in lysis buffer and sonicated. Resulting lysate was centrifuged and supernatant left to incubate overnight at 4 °C with Dynabeads, conjugated with anti-FLAG antibodies. The bound fraction was eluted, with TRIzol and chloroform, followed by RNA purification using Zymo RNA Clean & Concentrator Kit.
- Excision assay "with CboTnpA. To monitor excision MG1655 cells were transformed with TnpA expressing plasmid. The obtained transformants were used to make chemically competent cells that were then transformed with donor DNA containing plasmid. Doubletransformants were plated on LB agar with selective antibiotics and IPTG for the induction of TnpA expression. Resulting colonies were scraped from the plate and lysed by boiling at 95 °C for 10 min. The lysate was centrifuged, and the supernatant was used for PCR [0279] Splicing assay of CboIStron. Cells expressing CboIStron were grown until they reached exponential phase.
- FIG. 14A To test whether CboTnpB is able to cleave double-stranded DNA in E. coli a plasmid interference assay was designed (FIG. 14A). E. coli was transformed with a pEffector plasmid (encoding CboTnpB and coRNA), and then transformed with pTarget plasmids. When the target is recognized and cleaved, bacteria lose resistance to antibiotic encoded by pTarget. CboTnpB DNA cleavage utilized both TAM and mRNA guide complementarity to the target sequence (FIG. 14B).
- TnpB proteins have a predicted RuvC nuclease domain, which is also found in widely studied class II CRISPR-Cas nucleases (Cas9 and Casl2). By mutating one of its active site residues CboTnpB loses its activity confirming that DNA cleavage is RuvC-dependent (FIG. 14C).
- FIG. 15 A A similar experimental setup was used, but instead of a single pTarget a plasmid library that has a degenerate 6N nucleotide sequence was used. The coRNA guide sequence was also changed to be complimentary to the sequence downstream of the 6N motif (FIG. 15B). By plating on selective media and harvesting the surviving clones, the most depleted library members were identified by NGS.
- CboIStron exhibits self-splicing in E. coli Due to their left and right end similarity to group I introns, IStrons are predicted to be silent mobile genetic elements, capable of cleaving themselves out of RNA transcript (FIG. 16A).
- a minimal IStron lacking tnpA and tnpB genes
- RT-PCR was performed to capture splicing products.
- coRNA predicted IStron right end
- CboTnpA can excise IStron from its genomic location Just as the self-splicing activity can remove IStron from RNA transcript, so can CboTnpA permanently excise the element form any gene at the DNA level and integrate it elsewhere (FIG. 17 A).
- the activity of CboTnpA was reconstituted in E. coli and monitored excision by doing PCRto amplify the excision junction.
- CboTnpA effectively excised minimal IStron, but the effect was lost when IStron encoded CboTnpB (FIG. 17B).
- Example 6 Methods for programmable RNA-guided DNA cleavage using TnpB homologs
- Cas9- or Casl2-like nucleases with an associated guide RNA (sometimes referred to as gRNA or sgRNA). These nucleases are guided to a target site complementary to their respective sgRNA and generate DNA double strand breaks (DSBs) at the target site.
- a ssDNA or dsDNA donor template may be introduced as well for homologous recombination to occur, leading to the knock-in of a desired DNA sequence.
- thermophilic species lend further opportunities for improved genome editing, as thermostable systems show improved behavior in human cells.
- TnpB and IscB proteins derived from G. stearothermophilus are appealing nucleases for genome editing given their small reading frame and potential thermostability.
- TnpB and IscB proteins exhibited a range of detectible editing efficiencies across target sites at the HEK3 locus. Editing efficiencies are reported in FIG. 18.
- TnpB derived from ISGstJ
- TnpB derived from lSGst4
- TnpB Insertion sequences are compact and pervasive transposable elements found in bacteria and archaea, which canonically encode only the genes for their mobilization and maintenance. 1S200/YS605 transposons undergo ‘peel-and-paste’ transposition catalyzed by a TnpA transposase, but intriguingly, they also encode diverse, TnpB- and IscB-family proteins that are evolutionarily related to the CRISPR-associated effectors Cast 2 and Cas9, respectively. TnpB-family enzymes function as RNA-guided DNA endonucleases, but the broader biological role and their associated activity with TnpA has remained enigmatic.
- TnpA and TnpB to direct targeted double-stranded breaks
- DSBs double-stranded breaks
- the hyperrecombination frequency mediated by the TnpA transposase can be used to increase DSB- dependent site-specific recombination, overcoming limitations in the low efficiency of DSB- dependent recombination for site-specific DNA integration.
- TnpA increases site-specific DNA recombination following DSBs.
- 'LS200HS605 elements encode two genes: tnpA, which encodes a transposase containing a catalytic tyrosine residue responsible for DNA excision and integration of the mobile genetic element; and tnpB or iscB, which encode RNA-guided DNA nucleases termed TnpB or IscB. While the function of each gene in separation has been determined, the role of these proteins in combination has been unknown.
- IS200/IS605-like elements couple TnpA-mediated excision, resulting in a scarless excision event, with TnpB RNA-guided DNA cleavage, that targets the excised element during transposition, leading to DNA recombination and reinstallation of the IS element back into the donor site.
- An assay was developed to monitor recombination events occurring between a plasmid-encoded IS element inserted into full-length lacZ, and its corresponding lacZ donor joint site encoded on the genome (FIG. 30A).
- the incorporation of IS200ZIS605 transposon ends into a pDonor substrate, which also contains additional homology arms at integration sites facilitates the stimulation of DNA recombination reliant on double-strand breaks (DSBs).
- DSBs double-strand breaks
- This technique can be applied to various cell types, including bacterial cells, plant cells, animal cells, and human cells.
- mammalian cells can be transfected with a sequence of interest for DNA insertion, accompanied by TnpA and a DNA nuclease capable of inducing site-specific DSBs, thereby enabling site-specific recombination at the DSB site.
- the DNA nuclease may comprise CRISPR/Cas effectors (e.g., Cas9 or Casl2), RNA-guided DNA nucleases encoded by insertion sequences (e.g., IscB, IsrB, TnpB, or Fanzor), or homing endonucleases (e.g., ISce-I, ICre-I, HO).
- CRISPR/Cas effectors e.g., Cas9 or Casl2
- RNA-guided DNA nucleases encoded by insertion sequences e.g., IscB, IsrB, TnpB, or Fanzor
- homing endonucleases e.g., ISce-I, ICre-I, HO.
- the IS200/IS605 transposon ends utilized do not include stop codons and incorporate reading frames or linker sequences (such as glycine-serine linkers). These modifications facilitate the insertion of cargo payloads in-frame, into a target gene of interest, resulting in seamless fusions at the protein level with custom polypeptide sequences encoded by the cargo. Consequently, it becomes feasible to append a sequence of interest to a specific protein within the genome.
- linker sequences such as glycine-serine linkers
- Example 8 DNA transposition, RNA self-splicing, and RNA-guided DNA cleavage by multi-functional transposable elements
- TnpB Database was previously curated as described above. There, homologs of TnpB proteins were comprehensively detected using the J7. pylori (HpyTnpB) TnpB amino acid sequence (NCB1 Accession: WP_078217163.1) and a G. stearothermophilus TnpB amino acid sequence (NCBI Accession: WP_047817673.1) as seed queries for two independent iterative JackHMMER (HMMER suite v3.3.2) searches against the NR database (retrieved on 06/11/2021), with an inclusion and reporting threshold of le-30.
- HpyTnpB TnpB amino acid sequence
- NCBI Accession: WP_047817673.1 G. stearothermophilus TnpB amino acid sequence
- Group I Intron The initial search for group 1 introns associated with TnpB was performed using the Group I Intron Sequence and Structure Database models of available subclasses, refined by Nawrocki et al. 2018 (Nucleic Acids Res. 2018 Sep 6;46(15):7970-7976) and Zhou etal. 200 ⁇ S(Nucleic Acids Res. 2008 Jan;36(Database issue):D31-7). The 14 Group I intron subclass models were searched against all identified TnpB associated contigs with cmscan (Infernal vl .1.4).
- sequences 200 bp downstream and 50 bp upstream of the last nucleotide of the TnpB ORF were extracted to define the RE and transposon boundaries.
- the ⁇ 150-bp sequences were clustered by 99% length coverage and 99% alignment coverage using CD-HIT to remove duplicates.
- the remaining sequences were then clustered again by 95% length coverage and 95% alignment coverage using CD-HIT. This was done to identify clusters of sequences that were closely related but not identical, as expected of IS elements that have recently mobilized to new locations.
- TnpB and Arc-like ORF For TnpB found in putative IStron elements, protein sequences were clustered at 95% length coverage and 95% alignment coverage using CD-HIT. The clustered representatives were taken and aligned using MAFFT (v7.508) with the E-INS-I method for 16 rounds. Post-alignment cleaning consisted of using trimAl(vl.4.revl5) to remove columns containing more than 99% of gaps and manual inspection. The phylogenetic tree was created using IQ-Tree 2(v2.1.4) with a model of substitution identified using ModelFinder, and optimized trees with nearest neighbor interchange to minimize model violations. Branch support was evaluated with 1000 replicates of SH-aLRT, aBayes, and ultrafast bootstrap support from the IQTREE package. The tree with the highest maximum likelihood was used as the reconstruction of the IStron TnpB phylogeny.
- Group I Introns For all the group I intron hits from the search against the NT database, hits smaller than 300 bp were removed. The remaining sequences were clustered at 90% length coverage and 90% alignment coverage using CD-HIT. The clustered representatives were taken and aligned using MAFFT (v7.508) with the E-INS-I method for 2 rounds. Postalignment cleaning consisted of using trimAl (vl.4.rev!5) to remove columns containing more than 99% of gaps and manual inspection. The phylogenetic tree was created using IQ-Tree 2 (v2.1.4) with a model of substitution identified using ModelFinder, and optimized trees with nearest neighbor interchange to minimize model violations.
- Branch support was evaluated with 1000 replicates of SH-aLRT, aBayes, and ultrafast bootstrap support from the IQTREE package. The tree with the highest maximum likelihood was used as the reconstruction of the group I intron phylogeny. Neighborhood analysis was performed similarly to how the Arc-like ORFs were analyzed.
- Clostridia strain encoding IStrons with similarity of ⁇ 80% to C6oIStron was obtained from ATCC (strain 25772), where it was defined as belong to an unknown species classification. Internal rRNA phylogenetic analysis led to the assignment of this strain as a member of species senegalense.
- Clostridia senegalense was cultured from a lyophilized ATCC pellet in 5 mL of Gifu Anaerobic Medium Broth, Modified (mGAM; HyServe, 05433) under anaerobic conditions (5% Hi, 10% COi and 85% Ni) in an anaerobic chamber. All media was pre-reduced for ⁇ 24h before use in culturing. C.
- RNA from the Clostridia senegalense cell pellets were extracted in 96-well format using a silica bead beating-based protocol adapted from a prior study. Briefly, 200 pl 0.1 mm Zirconia Silica beads (Biospec, 11079101Z) were added to each well of 96-well deep- well plates (Thermo Fisher Scientific, 07-202-505). Next, cell pellets were resuspended in 500 pL DNA/RNA shield buffer (Zymo) and transferred to each well and the plates were affixed with a sealing mat (Axygen, AM-384-DW-SQ) and centrifuged for 1 minute at 4,500 g.
- a sealing mat Axygen, AM-384-DW-SQ
- the plates were vortexed for 5 seconds and incubated at -20 °C for 10 minutes before beating. Then, plates were fixed on a bead beater (Biospec, 1001) and subjected to bead beating for 5 minutes, followed by a 10 minute cooling period. The bead beating cycle was repeated three times total and plates were the centrifuged at 4,500 x g for 5 minutes to spin down cell debris. Next, 60% of the bead beating volume was transferred to the Zymo Miniprep Plus kit (Cat. No. R1057) and RNA was purified using the manufacturer’s protocol for gram positive bacteria.
- RNA quality was assessed using the 260/280 nm ratio ( ⁇ 2.0) as measured by Nanodrop (Cat No.) and concentration was measured by the Qubit RNA High Sensitivity Assay Kit (Cat. No. Q32852) using the manufacturer’s protocol. RNA was stored at -80 °C until library preparation.
- RNA-seq library preparation 10 pg of purified RNA was treated with Turbo DNase I (Thermo Fisher Scientific) for Ih at 37 °C using the manufacturer’s protocol. A 2X volume of Mag-Bind TotalPure NGS magnetic beads (Omega) was added to each sample and the RNA was purified using the manufacturer's protocol. The RNA was then diluted in NEBuffer 2 (NEB) and fragmented by incubating at 92 °C for 1.5 minutes.
- NEBuffer 2 NEB
- RNA with 5’ monophosphate and 3’ hydroxyl ends samples were treated with RppH (NEB) supplemented with SUPERase*ln RNase Inhibitor (Thermo Fisher Scientific) for 30 min at 37 °C, followed by T4 PNK (NEB) in IX T4 DNA ligase buffer (NEB) for 30 min at 37 °C. Samples were column- purified using RNA Clean & Concentrator-5 (Zymo) and the concentration was determined using the DeNovix RNA Assay. [0314] For sRNA-seq, a protocol was adapted for Clostridia senegalense from a prior study.
- RNA pellets were air-dried for 10 minutes at room temperature and dissolved in 20 pL of nuclease-free ultra-pure water. Samples were immediately put on ice or stored at -80 °C.
- Genomic DNA purification kit following the manufacturer’s protocol for gram-positive bacteria. DNA was measured by fluorescent quantification. TnY, a homolog of Tn5, was purified in-house following previous methods. lOng of purified gDNA was tagmented with TnY preloaded with Nextera Read 1 and Read 2 oligos, followed by proteinase K treatment (NEB, final concentration 16 units per mL) and column purification. PCR amplification and Illumina barcoding was done for 13 cycles with KAPA HiFi Hotstart ReadyMix; the PCR reaction was then resolved on a gel, and a smear from 400 bp to 800 bp was extracted for sequencing on a paired end, 150x150 NextSeq kit. Downstream analysis was performed as described in total RNA sequencing. De novo genome assembly was also performed by Plasmidschul, and the assembled genome was in agreement with the 4 Mbp genome provided for ATCC 25772.
- This forward oligo had all necessary sequences for Illumina sequencing. After 15 cycles of PCR under the same conditions, the reaction was resolved on a gel, and a smear from 350bp to 800bp was extracted for sequencing with at least 75 Read 1 cycles. After adapter trimming, the relative abundance of reads that contain a 20 bp sequence of the IStron end or contain a 20 bp sequence of the downstream genomic sequence were tallied using BBDuk from the BBTools suite (v.38.00; sourceforge.net/projects/bbmap) with a hamming distance of 2 and an average Qscore greater than 20.
- RNA-seq data were processed using cutadapt v4.2 to remove adapter sequences, trim low-quality ends from reads, and exclude reads shorter than 18 bp.
- Reads were mapped to the reference genome (Cdi: NZ CP010905.2; Cse: ATCC 25772) using the splice-aware aligner STAR v2.7.10, with — outFilterMultimapNmax 10. Mapped reads were sorted and indexed using SAMtools vl.17. Splice junctions inferred by STAR flanking loci of interest were used to create a custom genome annotation file for a second round of STAR alignment in order to refine spliced read counts.
- Sashimi plots showing read coverage and spliced reads at specific loci were generated with ggsashimi vl.1.5 in strand-specific mode.
- reads were mapped to a mock reference sequence spanning either the 5’ exon-intron junction, 3’ exon-intron junction, or the exon-exon junction.
- Reads mapping to each junction were quantified using featureCounts v2.0.2, with a minimum overlap of 3 bp on either end of the junction. Splicing activity was calculated as the number of reads mapping to the exon-exon junction divided by the average of reads mapping to the exon-intron junctions.
- E. coli str. K-12 substr. MG1655 (sSLOSlO) was transformed with 3xFLAG-CboTnpB (pSL5412) or 3xFLAG-CboTnpB(D189A) (pSL5413) and coRNA encoding plasmids.
- Single colonies were inoculated in liquid LB with spectinomycin (100 ⁇ g ml -1 ) and grown overnight. Next day the culture was inoculated at 100x dilution in 50 ml of liquid LB with spectinomycin (100 ⁇ g ml -1 ) and grown until ODeoo reached 0.5.
- Antibodies for immunoprecipitation were conjugated to magnetic beads as follows: for each sample, 30 pl Dynabeads Protein G (Thermo Fisher Scientific) was washed 3x in 1 ml RIP lysis buffer (20 mM Tris-HCl pH 7.5, 150 mM KC1, 1 mM MgCh, 0.2% Triton X-100), resuspended in 1 ml RIP lysis buffer, combined with 10 pl anti-FLAG M2 antibody, and rotated for >3 h at 4 °C. Antibody-bead complexes were washed an additional 3x to remove unconjugated antibodies, and were resuspended in 30 pl RIP lysis buffer per sample.
- each sample was combined with 30 pl antibody-bead complex and rotated overnight at 4 °C. The next day, each sample was washed 3x with ice-cold RIP wash buffer (20 mM Tris-HCl pH 7.5, 150 mM KC1, 1 mM MgCh). After the last wash, beads were resuspended in 1 ml TRIzol (Thermo Fisher Scientific) and incubated at RT for 5 min to allow separation of RNA from the beads.
- RNA concentration was quantified using the DeNovix RNA Assay.
- Illumina sequencing libraries were prepared using the NEBNext Small RNA Library Prep kit, and libraries were sequenced on an Illumina NextSeq 500 in paired-end mode with 75 cycles per end.
- Native IStron, IStron with TnpB only and mini-IS sequence (581 bp from the right end and 221 bp of the right end) were cloned using Gibson assembly, by inserting them into a pCDF-duet vector downstream of T7 promoter.
- pTarget plasmids were generated by around-the-horn PCR, inserting 44-bp a target sequence into a minimal pCOLDA-Duet-1 vector.
- Transposition intermediate (pDonorCI) was generated by Gibson assembly of C6oIStron left end (581 bp), right end (221 bp), R6K ori and chloramphenicol resistance gene.
- Cloning mix was transformed to pir+ strain, to allow for the propagation of R6K ori bearing plasmid.
- Derivatives of these plasmids were cloned using a combination of methods, including Gibson assembly, restriction digestion-ligation, ligation of hybridized oligonucleotides, Golden Gate Assembly and around-the-horn PCR. Plasmids were cloned, propagated in NEB Turbo cells (NEB) (except for pCircInt derivatives, which were propagated in pir + strain), purified using Miniprep Kits (Qiagen), and verified by Sanger sequencing (GENEWIZ).
- Plasmid interference assays were performed in E. coli str. K-12 substr. MG1655 (sSLOSlO) when synthetic CboTnpB expression construct was used, and in E. coli BL21 (DE3) strain for all other experiments.
- C6oTnpB was co-expressed with ⁇ RNA from the same plasmid
- BL21 (DE3) cells were transformed with a pEffector plasmid, and single colony isolates were selected to prepare chemically competent cells. 200 ng of pTarget plasmid were then delivered via transformation. After 2 h, cells were spun down at 6000 rpm for 5 min and resuspended in 30 pl of LB.
- Cells were then serially diluted (10x) and plated on LB agar media containing spectinomycin (100 ⁇ g ml -1 ) and kanamycin (50 ⁇ g ml -1 ) and grown for 24 h at 37 °C. Plates were imaged in an Amersham Imager 600.
- mini-IS was used as a guide for CAoTnpB
- BL21 (DE3) cells were co-transformed with mini-IS and TnpB expression plasmids, and single colony isolates were selected to prepare chemically competent cells.
- Second transformation was performed as indicated previously, and cells were plated on LB agar media containing spectinomycin (100 ⁇ g ml -1 ) , chloramphenicol (25 ⁇ g ml -1 ) , kanamycin (50 ⁇ g ml -1 ) and IPTG (0.1 mM) and grown for 24 h at 37 °C. Plates were imaged in an Amersham Imager 600.
- E. coli str. K-12 substr. MG1655 was transformed with TnpA expression plasmid and selectively grown on LB with kanamycin (50 ⁇ g ml -1 ).
- a single colony was used to make chemically competent cells, which were then transformed with 100 ng mini-IS element encoding plasmid.
- Cultures were grown overnight at 37 °C on LB-agar with spectinomycin (100 ⁇ g ml -1 ), kanamycin (50 ⁇ g ml -1 ) and IPTG (0.5 mM) for TnpA induction. Scraped colonies were resuspended in LB medium.
- Plasmids with an R6K ori, a CmR marker, and inverted IStron ends were cloned in pir+ strains.
- E. coli str. K-12 substr. MG1655 was transformed with a pLac-TnpA expression plasmid and various pDonorCI variants via electroporation, recovered for 7 hours, plated on LB Agar plates with chloramphenicol, and grown for ⁇ 24 hours.
- Surviving colonies were pooled and genomic DNA was extracted and quantified via Qubit Approximately 100 ng of gDNA was tagmented with TnY, pre-loaded with Read 2 Nextera oligos.
- sSL3391 a derivative of E. coli str. K-12 substr. MG1655 with a lacZ deletion replaced by a chloramphenicol resistance cassette
- pSL4825 empty vector
- pSL5948, pSL5949, pSL5950 CboIStron-interrupted lacZ gene
- Cells were grown at 37 °C for 36 hours, then harvested, serially diluted, and plated onto LB agar containing tetracycline (10 ⁇ g ml -1 ) and X-gal (200 ⁇ g ml -1 ) and grown for 18 h at 37 °C. Total number of colonies were counted, along with the number of blue colonies to determine the frequency of excision and reintegration events. In addition, genomic lysate was harvested from cells as described above for PCR analysis.
- E. coli str. K-12 substr. MG1655 (sSL0810) containing an intact lacZ loci were chemically transformed with 400 ng of plasmid encoding an intact lacZ gene (pSL4825, empty vector) or CioIStron-interrupted lacZ gene (pSL5948, pSL5949, pSL5950), recovered for 1 h at 37 °C in liquid LB, and serially diluted on LB-agar plates with tetracycline (10 pg ml" 1 ). Next day colonies were counted and converted to CPUs per pg of DNA.
- Tetracycline plates were then replica plated to LB-agar plates containing both tetracycline (10 pg ml" 1 ) and X-gal (200 pg ml" 1 ) for blue/white colony screening. White colonies were counted to determine the frequency of recombination events at the genomic lacZ locus.
- Templates for in vitro splicing reactions were obtained by PCR amplification of Marker (mock excised), splicing mutant and mini-IS containing plasmids. All templates had a T7 promoter encoded within the plasmid, which is required for transcription. PCR products were extracted from gel and 1 pg of each was used in 50 pl in vitro transcription reaction.
- In vivo splicing assays were performed in E. coli BL21 (DE3) strain transformed with mini-IS variant encoding plasmid, or co-transformed with mini-lS and TnpB expression plasmids. For single plasmid transformations, single colonies were picked from a plate and inoculated to grow overnight in LB with spectinomycin (100 ⁇ g ml -1 ).
- the cultures were re-inoculated at 40x dilution in LB supplemented with spectinomycin (100 ⁇ g ml -1 ) and IPTG (0.1 mM), and grown until ODeoo reached 0.5-0.7. Then an aliquot equivalent to 250 pl of cell suspension at ODeoo was taken from each culture, centrifuged at 6000 rpm for 5 min and cell pellet resuspended in 750 pl Trizol (Thermo Fisher Scientific). After incubating 10 min at room temperature 150 pl of chloroform was added, tubes shaken and centrifuged at 12,000 g for 15 min at 4 °C.
- RNA was stored at -80 °C.
- splicing assays with TnpB co-expressed in trans single colonies were inoculated to grow overnight in LB with spectinomycin (100 ⁇ g ml -1 ) and chloramphenicol (25 ⁇ g ml -1 ).
- the cultures were re-inoculated at 40x dilution in LB supplemented with spectinomycin (100 ⁇ g ml -1 ), chloramphenicol (25 ⁇ g ml -1 ) and IPTG (0.5 mM), and grown until ODeoo reached 0.5-0.7. All downstream steps were performed as described before.
- RNA was used as an input for reverse transcription reaction.
- total RNA was treated with 1 pl dsDNase (Thermo Fisher Scientific) in 1 x dsDNase reaction buffer in the final 10 pl volume, incubating at 37 °C for 20 min.
- 1 pl of 10 mM dNTP, 1 pl of 2 mM IStron-interrupted gene-specific primer and 1 pl of 2 mM SpecR specific primer were added for gene-specific priming and reactions were heated at 65 °C for 5 min.
- Incubation was stopped by placing the tubes directly on ice, followed by addition of 4 pl of SSIV buffer, 1 pl 100 mM DTT, 1 pl SUPERase*InTM (Thermo Fisher Scientific) and 1 pl of SuperScript IV Reverse Transcriptase (200 U/pl, Thermo Fisher Scientific) and incubation at 53 °C for 10 min and 80 °C for 10 min.
- the resulting cDNA was diluted and used for end-point or quantitative PCR. Endpoint PCR was performed in a 20 pl reaction volume containing 1 x OneTaq Master Mix (NEB), 0.2 pM of each primer and 1 pl of 100-fold diluted cDNA.
- TnpA and TnpB homologs are encoded within group I introns, generating chimeric genetic elements called IStrons. These elements are not only mobile on the DNA level, due to TnpA and TnpB, but are phenotypically silent on the RNA level because the whole element is removed during splicing. IStrons can harbor TnpA and TnpB proteins related to either IS605 or IS607, suggesting multiple IS element acquisition events by group I intron during evolution. Some of the IStrons encoding proteins from IS607 elements were found in pathogenic bacteria species of Clostridium botulinum. Under low-oxygen conditions these bacteria produce highly dangerous toxins that block nerves and cause muscle and nerve paralysis.
- TnpB TnpB
- CboTnpB TnpB
- RuvC active site The same active site is also responsible for coRNA maturation on the 5’ end.
- Transposase (CboTnpA) associated with this TnpB recognizes CboIStron ends and can excise the element from its native location. Lastly, the CboIStron can self-splice from the E.
- TnpA derived from IS607-family transposons represents a serine-family recombinase, hereby indicated by the suffix "(S)" to signify its serine catalytic active site. Contrarily, the previously published Meers work on TnpA corresponds to a tyrosine-family recombinase, distinctly referenced as TnpA(Y), emphasizing its tyrosine catalytic active site. These designations, "(S)” and “(Y)”, underscore the differentiation between these enzyme families or classes of transposons.
- TnpB mRNA sequence was defined and some primary sequence elements can be changed while preserving the structural fold of the RNA (e.g., complementary mutations for the pseudo-knot shown in FIG. 33D).
- Some structural features of toRNA can be removed (e.g., FIG. 34D, removal of SL4) to attenuate C6oTnpB activity, suggesting that alterations to raRNA can be made to modulate TnpB activity.
- TnpB derived from C. botulinum originates from the IS607-family elements.
- IS607- family elements represent a distinct evolutionary lineage, separate from the IS200/IS605-family transposons.
- RNA splicing activity can be repressed in the presence of TnpB.
- Different intron sequence elements differ in their susceptibility for TnpB repression (Fig. 33F). It could be possible to have multiple similar copies of the same element in a cell or genome, which would differ only in their right-end encoded oiRNA portion, which is recognized by TnpB. Only the IStron elements that have a TnpB-binding competent oiRNA would be expected to be recognized and their splicing selectively repressed by TnpB.
- IStrons may serve as platforms for introducing selection markers, facilitating their placement within any gene, even those categorized as essential. As evidenced, IStrons can splice at the RNA level, resembling the characteristics of group I introns. When DNA segments containing drug markers are situated within the IStron boundaries, encompassing both the left and right ends crucial for excision and splicing, a seamless genomic integration is achieved, ensuring the original function of the host gene remains undisturbed. This enables the expression of the drug marker, facilitating selection, while concurrently ensuring that RNA splicing remains unaffected, thus preserving the unaltered function of the gene in question. Upon the need for marker elimination, TnpA is engaged.
- the IS element can be seamlessly integrated into a wide spectrum of heterologous genomes, encompassing, but not limited to, bacteria, fungi, insects, and mammals, employing conventional genome editing techniques. Once integrated, the IS element adopts the role of an adaptive 'gene drive'. This process is aided by the TnpB or IscB, which, in complex with coRNA, utilize its intrinsic ability to initiate homologous recombination. This targets native sequences on either sister or homologous chromosomes, particularly those without the IS element.
- TnpA orchestrate the relocation of the IS element within a different genomic locale
- TnpB is equipped to spontaneously adapt and secure a novel guide for the coRNA, ensuring its sustained function in the new setting.
- This mechanism stands in contrast to the established Cas9-centric gene drive methodologies which necessitate a statically pre-defined sgRNA for locus-specific targeting.
- Such traditional sgRNAs lack the flexibility to adjust if their corresponding element relocates.
- the dynamic nature of TnpB/IscB-centric gene drives equips them with the adaptability to align with the immediate changes in their genomic surroundings
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